UV/EB curable butyl copolymers for lithographic and corrosion-resistant coating applications

ABSTRACT

A lithographic coating and method of framing a lithographic image are disclosed. The method comprises coating at least a portion of a surface of an article with a radiation-crosslinkable polymer, and exposing the coated surface to a pattern of radiation to crosslink the polymer in a lithographic image. The functionalized polymer is a copolymer of an isoolefin of 4 to 7 carbon atoms and para-alkylstyrene, wherein the para-alkylstyrene is functionalized with a radiation reactive group at the para-alkyl group of the para-alkylstyrene.

This is a divisional application of U.S. Ser. No. 08/298,450, filed onOct. 27, 1994, which is a divisional application of U.S. Ser. No.07/982,104, filed on Nov. 24, 1992, now U.S. Pat. No. 5,376,503, whichis a continuation application of U.S. Ser. No. 07/631,610, filed Dec.20, 1990.

FIELD OF THE INVENTION

This invention relates to ultraviolet (UV) and electron beam (EB)reactive functionalized copolymers of isoolefin and para-alkylstyreneformulated into lithographic, corrosion resistant and other coatings.More particularly, this invention relates to such copolymers, coatingsand methods wherein the para-alkylstyrene is functionalized to impartradiation curability.

BACKGROUND OF THE INVENTION

The use of radiation-sensitive functionality to induce crosslinking of apolymeric material is an advancing art, especially in the photographicindustry where photographic films are composed of polymers having lightsensitivity. However, it is also desirable to incorporate EB- orUV-crosslinkable functionality into elastomeric polymers. Elastomerscontaining such functionality could be utilized in pressure-sensitiveadhesives (PSA's) and coatings to impart radiation curability, adhesivestrength, and enhanced resistance to temperature, abrasion, solvents andozone.

Applications employing external crosslinking reagents have certaininherent difficulties: such compositions require processing of thepolymer with photoinitiators or crosslinking agents to facilitate thecuring process. The toxicity and volatility of these compounds canpresent manufacturing difficulties and hazards. PSA's and coatings canhave highly reactive unsaturation sites in the polymeric backbone tofacilitate external free-radical crosslinking, but depending on thepolymer, the unsaturation also provides sites at which the backbone canbe degraded by reactions involving radicals.

U.S. Pat. No. 4,556,464 to St. Clair discloses a radiation curableadhesive composition suitable for use as a PSA, comprising a blockpolymer ABA formulation, where block A is polystyrene/isoprene orpolystyrene/butadiene copolymer and block B is polyisoprene, a tackifiercompatible with block B and a crosslinking agent compatible with blockA.

It is desirable to have PSA's and coatings which are curable without theuse of these additive compounds and have saturated polymeric backboneswhich are not degraded in reactions involving radicals. Therefore,radiation-reactive crosslinking agents may alternatively be incorporatedinto the polymer backbone, for instance, by copolymerizing with aradiation-sensitive vinyl polymerizable comonomer. Preparing suchcomonomers on a large scale is generally difficult. Radiation-reactivefunctionality may also be grafted onto the polymer backbone in apost-polymerization step, however, the resulting polymer is typically aheterogeneous product of low yield due to the difficulty of achievingadequate molecular contact at desired reaction sites. A good discussionof the mechanisms of photochemical reactions in polymers and examples ofphotoinitiators may be found in J. F. Radek, "Mechanisms ofphotophysical Processes and Photochemical Reactions in Polymers Theoryand Applications," Chapters 11 and 12, J. Wiley & Sons, 1987, which ishereby incorporated herein by reference.

European patent application 17,364 discloses copolymers curable byactinic radiation, such as UV light, made by incorporating from 0.1 to10 percent by weight of the copolymer of an allyl benzoylbenzoatecomonomer with a polymerizable monoethylenically unsaturated comonomer.These polymers are said to be useful in coating and impregnatingformulations, and in adhesive, caulk and sealant formulations.

U.S. Pat. No. 4,315,998 to Neckers et al. discloses polymeric materialswhich incorporate photosensitive functionality via a nucleophilicsubstitution reaction. The polymeric materials serve as a platform forheterogeneous catalysts for a variety of photoinitiated chemicalreactions.

U.S. Pat. Nos. 4,188,215 to Sato et al.; 3,923,703 to Fukutani et al.;3,867,318 to Nishikubo etal.; 3,694,383 to Azami et al.; and 3,560,465to Reynolds; and U.K. Patent 1,341,004 all relate to polymeric resinsincorporating photosensitive functionality and/or processes for makingsuch resins. These photosensitive resins are generally useful inphotographic films.

Photosensitive coatings comprising a blend of a polymer and aphotosensitive crosslinking agent are disclosed in U.S. Pat. No.3,867,271 to Malatesta, etal. In this patent, a conjugated dienecontaining butyl rubber is cured by ultraviolet radiation with the aidof certain photosensitizers. A similar composition said to be useful asa coating for glass substrates is disclosed in U.S. Pat. No. 4,086,373to Tobias etal., as comprising at least a rubbery thermoplastic organicpolymer and an organic photosensitizer.

Photosensitive vinyl monomers are disclosed in U.S. Pat. Nos. 3,429,852and 3,574,617 both to Skoultchi, wherein ethylenically unsaturatedderivatives of substituted benzophenones are prepared by a methodinvolving reacting a substituted benzophenone with an ethylenicallyunsaturated reagent such as glycidyl acrylate or glycidyl methacrylate.The resulting monomers may thereafter be homo- or copolymerized with avariety of conventional ethylenically unsaturated, i.e. vinyl, monomers.Photosensitive coating systems are prepared by depositing a solidpolymer from an organic solvent or an emulsion onto a substrate. Thephotosensitive coating are said to be particularly suitable for use invarious applications including, for example, lithography and chemicalmilling.

A similar concept is disclosed in U.S. Pat. No. 4,148,987 to Winey,wherein monoethylenically unsaturated derivatives of substitutedbenzophenones or acetophenones are prepared by a reaction of thebenzophenone or acetophenone with a vinyl benzyl halide. Thesederivatives are polymerizable to form homopolymers, or copolymers with awide variety of conventional ethylenically unsaturated monomers. Theresulting polymers are sensitive to radiation, such as ultraviolet lighthaving a wave length of 2,000 to 5,000 angstroms, and readily crosslinkor cure upon exposure to such radiation. Adhesives, binders, coatingsand impregnating compositions are made from the polymers.

Radiation-sensitive functionality have also been used to inducecrosslinking of a polymeric material in the printing industries whereprinting plates are initially coated with polymers having lightsensitivity. Such radiation-crosslinkable polymers have also been widelyused as photoresists in the manufacture of semi-connectors or otherengraved articles.

A process by which a polymer is functionalized with radiation-curablemoieties is disclosed in U.S. Pat. No. 4,112,201 to Jones, whereinbutadiene or isoprene copolymers having pendent unsaturatedtetra-aliphatic quaternary nitrogen moieties, such as those derived fromacrylic esters and acrylamides are useful as water soluble or inherentlywater-dispersable curable coatings. Such coatings are useful asprotective and/or decorative coatings, paper coatings, textile fibercoatings, printing plates, photocurable imagable materials inphotoresists, lithographic plates, etc. The coatings are said to becurable with light, with high energy radiation and with heat in thepresence of free-radical catalysts to form insoluble crosslink coatings.The polymers are prepared by amination and a post-polymerizationreaction. Likewise, the chemical modification ofpoly(vinylbenzylchloride) with a photosensitive compound includingp-hydroxybenzophenone, 2-hydroxyfluorenone, potassium carbazole, and thelike is disclosed in Bailey, et al., Journal of Applied Polymer Science:Polymer Chemistry Edition, vol. 17, 777-782 (1979).

In Azuma et al., Journal of Applied Polymer Science; Polymer ChemistryEd., vol. 18, 781-797 (1980), the properties and preparation ofcis-1,4-polybutadiene and polypentenamer having pendant functionalgroups including cinnamoyl groups are disclosed. Cinnamoyl groups areintroduced into the polypentenamer, for example, by reacting apolypentenamer having hydroxymethyl groups with cinnamoyl chloride.Relationships involving the photosensitivity of cinnamoylatedpolypentenamer are discussed.

In Azuma etal., Journal of Applied Polymer Science, vol. 25, pp.1273-1286 (1980), there is described an addition reaction of anα,β-unsaturated carboxylic acid, such as cinnamic acid, to a polydiene,such as cis-1,4polybutadiene, 1,2-polybutadiene and polypentenamer, inthe presence of an acid catalyst. The unsaturated polydienes undergocyclization in competition with the incorporation of carboxylate groups.Polymer morphology was said to indicate block segments alternatingbetween cyclic segments and incorporated segments. The polymers werereported to have two glass transition temperatures, and the degree ofincorporation against cyclization thereof to be controllable by reactionconditions,

In Azuma etal., Journal of Applied Polymer Science, vol. 27, pp.2065-2078 (1982), there is disclosed a study conducted on the relationof photosensitive cyclized polydienes such as cis-1,4-polybutadiene, andpolypentenamer having pendent cinnamate groups to the polymer structure.Photodimerization of cinnamate groups was said to be greatly affected bythe mobility of the groups, while as the degree of cyclizationincreased, photosensitivity decreased.

From Azuma et al., Journal of Applied Polymer Science, vol. 28, pp.543-557 (1983), it is known to react polyisoprene in o-dichlorobenzenesolution with maleic anhydride to form polyisoprene modified withα-substituted succinic arthydride groups, and to further modify thepolyisoprene by reaction with hydroxyethyl cinnamate in pyridine toincorporate cinnamate groups. It was stated that up to 75 mole percentof the repeating groups could be easily incorporated photosensitivity ofthe modified polyisoprene was said to be greater than that of cinnamatemodified polypentenamer due to interaction of the free carboxylategroups. The interaction reduced the dependence of photosensitivity onmobility of polymer segments.

The preparation and use of copolymers of styrene and isobutylene isknown in the art. Thus, such copolymers ranging from tough, glassy highpolystyrene content copolymers for use in plastic blends, to rubbery lowstyrene content copolymers for use as impact modifiers, etc., havebecome well known in this art. Styrene and isobutylene have beencopolymerized rather readily in the past under cationic polymerizationconditions to yield these copolymers covering the entire compositionalrange. It is also known that blocky or random homogeneous copolymers canbe produced by altering the copolymerization conditions, such as shownin U.S. Pat. No. 3,948,868 to Powers. This patent thus describes theproduction of random homogeneous polymers comprising at least twocationically polymerizable monomers such as isobutylene and styrene.This disclosure also includes a lengthy list of various olefiniccompounds including isobutylene, styrene, α-methylstyrene and other suchcompounds. Furthermore, these compounds have been used in a variety ofapplications, including use as adhesives in connection with othermaterials taking advantage of the surface characteristics of thepolyisobutylene sequences, as coatings, as asphalt blends, and invarious plastic blends. As is discussed in the '868 patent, it is alsowell known to produce terpolymers including isoprene, but doing soreduces the overall polymer molecular weight rendering the production ofhigh molecular weight polymers therefrom difficult, and complicating theoverall production sequence,

There have also been attempts to produce various functionalizedpolymers. For example, U.S. Pat. No. 3,145,187 to Hankey et al.discloses polymer blends which include a vinyl chloride polymer, asurfactant, and a chlorinated olefin polymer, and the latter is said toinclude copolymers of various materials which can include isobutyleneand styrene, as well as ring-alkyl styrenes, among a large number ofother compounds, which olefin polymers can then be chlorinated by knownmethods.

The literature has also disclosed other routes for obtaining copolymersof isobutylene and styrene, such as that shown in U.S. Pat. No.4,074,034 to Powers et al. which discloses the copolymerization ofisobutylene with halomethylstyrene. This technique requires the use ofvinylbenzyl chloride and the like as starting material, and utilizes aspecified continuous solution process with solvent or mixed solventsystems in which the monomers are soluble under specified conditions.Aside from the need to employ the expensive vinylbenzyl chloridestarting material, these processes also have limitations in terms of thequantity of aromatic chloromethyl functionality which can beincorporated in this manner without encountering excessive chainbranching and gel formation during polymerization, and in terms ofpolymer recovery because of the reactivity of the benzylic chlorineunder cationic polymerization conditions. See, "Isobutylene Copolymersof Vinylbenzyl Chloride and Isopropenylbenzyl Chloride," Journal ofApplied Polymer Science, vol. V, Issue No. 16, pp. 452-459 (1969) inwhich the aromatic monomer is said to be a mixture of the para and metaisomers.

There has also been some interest in the halomethylation ofisobutylene/styrene copolymers, such as discussed in a paper by Sadykhovet al. entitled "Chloromethylation of an Isobutylenestyrene Copolymerand Some of Its Chemical Reactions," Acerb, Neft, Khoz., 1979 (6) 37-9.

In an article by Harris et al. entitled "Block and Graft Copolymers ofPivalolactone . . . ," Macromolecules, 1986, vol. 19, pp. 2903-2908, theauthors discuss the copolymerization of isobutylene with styrene andpreferably a ring-methylated styrene. This article specificallydiscloses copolymerization with vinyl toluene, comprising a mixture ofmeta- and para-methylstyrene in approximately 65/35 amounts, and withpara-methylstyrene, for the purpose of producing thermoplastic elastomerpivalolactone copolymer systems with no auto-oxidizable aliphaticunsaturation. The article fails to recognize any difference between theuse of vinyl toluene and para-methylstyrene, and in any event, even whenit employs the latter, it employs conditions which result in copolymershaving the properties, including heterogeneous compositionaldistribution and very broad molecular weight distribution for theunfractionated copolymer, as set forth in Tables 4 and 5, which includean M_(n) for the unfractionated copolymer of 16,000, M_(w) /M_(n) of17.45, and a 4-methylstyrene content in the polymer which variesconsiderably from the monomer feed and varies significantly as afunction of molecular weight.

Finally, there are also articles which discuss copolymers of isobutyleneand para-methylstyrene without discussing any method for preparing them.These articles include Sadykhov, et al., "Studies of Oxidative ThermalDegradation of Copolymers of Isobutylene with m- and p-Methylstyrenes ina Solution of Mineral Oils," Uch. Zap. Azerb. Un. t. Ser. Khum., 1975(304), 87-92, and other such articles. Furthermore, in Toman, et al.,"Isobutylene Polymers and Copolymers with Controlled Structure", App.78/7, 339, (Nov. 10, 1978), there is reference to the copolymerizationof isobutylene with vinyl aromatic monomers. The search has thuscontinued for useful molecular weight copolymers of isobutylene andalkyl styrene, and in particular for functionalized copolymers of thistype which can be cross-linked, and otherwise used in a variety ofapplications.

Polymers with a saturated hydrocarbon backbone are well known to possessgood environmental and aging resistance which makes them highlydesirable in a variety of applications. Furthermore, rubbery copolymerscontaining major amounts of polyisobutylene are well known to possesslow permeability, unique damping properties, and low surface energywhich makes them particularly highly desired in many applications.However, the "inertness" of these saturated hydrocarbon polymers, theirlow reactivity and incompatibility with most other materials, and thedifficulties in adhering them to, or using them in conjunction with mostother materials has restricted their use in many areas.

In commonly assigned U.S. Ser. No. 441,575, filed Nov. 22, 1989, whichis also a continuation-in-part of co-pending U.S. Ser. No. 416,503 filedOct. 3, 1989, which is a continuation-in-part of co-pending U.S. Ser.No. 199,665 filed May 27, 1988; and co-pending U.S. Ser. No. 416,713filed Oct. 3, 1989, which is a continuation-in-pan of U.S. Ser. No.199,665 filed May 27, 1988, the disclosures of which are herebyincorporated by reference, it was theorized that the introduction ofcontrolled amounts of the desired specific functionality as pendantgroups on the saturated hydrocarbon backbone would greatly extendusefulness by permitting these polymers to be adhered to other surfacesand/or to be co-reacted with or compatibilized with other functionalpolymers by "grafting" or crosslinking reactions. It was furthertheorized that the introduction of pendant functionality of the righttype and amounts would permit these saturated hydrocarbon polymers to be"painted" or coated with or on other materials, and/or to be laminatedwith or dispersed in other materials to yield composite materials with adesired combination of properties.

As has been already pointed out, the fact that benzylic halogenfunctionality constitutes a very active electrophile that can be converted to many other functionalities via S_(W) 2 nucleophilic substitutionreactions has long been recognized, and the chemical literature isreplete with examples of these reactions. Selective conversions in highyield to many functionalities, including the following have beenreported: aldehyde, carboxy, amide, ether, ester, thioester, thioether,alkoxy, cyanomethyl, hydroxymethyl, thiomethyl, aminomethyl, cationicionomers (quaternary ammonium or phosphonium, S-isothiouronium, orsulfonium salts), anionic ionomers (sulfonate and carboxylate salts ),etc. In addition, the literature described many examples in which abenzylic halogen is replaced by a cluster of other functionalities bynucleophilic substitution with a multifunctional nucleophile such as:triethanolamine, ethylene polyamines, malonates, etc.

Nearly all of this previous work has been with simple, small (i.e.non-polymeric) molecules containing the aromatic halomethyl (orbenzylic) functionality. However, a considerable amount of art alsoexists on nucleophilic substitution reactions involving chloromethylstyrone and polystyrenes containing aromatic chloromethyl groups tointroduce other functionalities. Much of this work involves reactionswith "styragels" or lightly crosslinked polystyrenes containing variousamounts of benzylic chlorine. While many of the same nucleophilicsubstitution reactions previously reported for small moleculescontaining benzylic chlorine have been achieved in "styragels," it hasbeen necessary to modify reaction conditions, and in particular to oftenemploy phase transfer catalysts, in order to promote the desiredsubstitution reaction. Reactions involving the benzylic chlorine inpolystyrene have been more difficult to achieve than in simple smallmolecules because of the greater difficulty in achieving the intimatecontact required between the reactants when one of the reactants (thearomatic chloromethyl moiety) is in a separate polymeric phase from theother reactant. Yields have also generally been lower and side reactionsare more prevalent in the reactions involving the benzylic chlorine inpolystyrene. However, since most of the work has been with "styragels,"it has generally not been necessary to achieve high conversion in"clean," highly selective substitution reactions in order to preservepolymer solubility. Good recent review of this work involvingchloromethyl styrene and "styragels" containing benzylic chlorines arein the literature. See Marcel Camps et al., in "Chloromethylstyrene:Synthesis, Polymerization, Transformation, Applications" in Rev.Marcromol. Chem. Physics, C22(3), pp. 343-407 (1982-83); JMJ Frechet inChemical Modification of Polymers Via Phase Transfer Catalysts in CrownEthers and Phase Transfer Catalysts in Polymer Science, edited byMatthews and Canechef and Published by Plenum Press, NY, 1984; andJean-Pierre Montheard et al., in "Chemical Transformations ofChloromethylated Polystyrene" in JMS-Rev. Macromol. Chem. Phys., C-28 (3& 4), pp. 503-592 (1988).

Previous workers have not applied nucleophilic substitution reactionsisobutylene/para-methylstyrene/para-bromomethylstyrene terpolymers toproduce versatile, substantially saturated, pendant functionalized,soluble copolymers.

SUMMARY OF THE INVENTION

The present invention is, in one aspect, the discovery of coatingcompositions suitable for use in various lithographic and corrosionbarrier applications comprising radiation curable copolymers. The term"radiation curable" refers to the vulcanization of the copolymer throughexposure to ultraviolet (UV), electron beams (EB), gamma, visible,microwave, and like radiation. The radiation curable copolymer comprisesa copolymer of an isoolefin of 4 to 7 carbon atoms and apara-alkylstyrene wherein radiation-reactive functional groups aresubstituted on the para-alkyl group. In one preferred embodiment, theisoolefin comprises isobutylene, and the para-alkylstyrene comprisespara-methylstyrene and/or radiation-curable functionalizedpara-methylstyrene. The copolymer can be internally crosslinkedutilizing UV or EB radiation and consequently requires no photoinitiatorreagent or crosslinking promoter.

In accordance with an embodiment of the present invention, aradiation-curable coating composition comprises the radiation-reactivefunctionalized copolymer. The radiation-reactive functionalizedcopolymer comprises an isoolefin having from 4 to 7 carbon atoms and apara-alkylstyrene wherein the copolymer has a number average molecularweight (M_(n)) of at least about 5000, preferably from about 5000 toabout 500,000 or greater, and more preferably from about 50,000 to about300,000. The radiation-reactive functionalized copolymers alsopreferably have a ratio of weight average molecular weight (M_(w)) toM_(n) of less than about 6, more preferably less than about 4, mostpreferably less than about 2.5.

In accordance with a preferred embodiment, the preferred functionalizedcopolymers employed in the lithographic or corrosion resistantcomposition and/or method of the present invention are elastomeric,radiation-reactive functionalized copolymers, comprising isoolefinbetween about 80 and 99.5 percent by weight of the copolymer andpara-alkylstyrene between about 0.5 and 20 percent by weight of thecopolymer, wherein the radiation-reactive functionalizedpara-alkylstyrene comprising between about 0.5 and 55 mole percent ofthe para-alkylstyrene. In accordance with another embodiment, however,where glassy or plastic materials are being produced as well, theradiation-reactive functionalized copolymers comprise isoolefin betweenabout 10 and 99.5 percent by weight of the copolymer, para-alkylstyrenebetween about 0.5 and 90 percent by weight of the copolymer andradiation-curable functionalized para-alkylstyrene between about 0.5 and55 percent by weight of the polymer. The coating composition preferablycomprises at least about 50 parts by weight of the radiation-reactivefunctionalized copolymer and from 0 to about 50 parts by weight of theradiation-inactive polymer wherein the parts by weight of the componentstotal 100.

In accordance with a preferred embodiment of the lithographic orcorrosion resistant composition and/or method of the present invention,the radiation-reactive functionalized copolymers include thepara-alkylstyrene having a radiation reactive functional group affixedto the alkyl group as: ##STR1## where in R and R' are independentlyselected from hydrogen, alkyl, and the primary and secondary alkylhalides, and Y is a radiation-reactive functional group or groups joinedto the copolymer via ether, ester, amine or other types of chemicalbonds. Preferably, these radiation-reactive functionalized copolymersare otherwise substantially free of any additional functional groups inthe form of any ring functional groups or any functional groups on thepolymer backbone chain (i.e., on the isoolefin carbons).

A precursor copolymer of isoolefin having between 4 and 7 carbon atomsand the para-alkylstyrene used for preparation of the radiationfunctionalized copolymers described above is formed by admixing theisoolefin and the para-alkylstyrene-in a copolymerization reactor undercopolymerization conditions in the presence of a diluent, and a Lewisacid catalyst, and maintaining the copolymerization reactorsubstantially free of impurities which can complex with the catalyst: orwhich can copolymerize with the isoolefin or the para-alkylstyrene. Inthis manner, precursor copolymers for making the above-describedradiation functionalized copolymers are produced as direct reactionproducts, which, in their as-polymerized form, have a substantiallyhomogeneous compositional distribution, and which can also consistessentially of isoolefin and para-alkylstyrene, and have a numberaverage molecular weight of greater than about 5000. Theisobutylene/para-methylstyrene precursor copolymer is insoluble in thepreferred diluent and the process is thus a slurry polymerizationprocess. In another embodiment, however, in which theisobutylene/para-methylstyrene precursor copolymer is soluble in thediluent, a solution polymerization process is described.

The precursor copolymer of the isoolefin and the para-alkylstyrene isthen partially selectively brominated to yield a "base terpolymer"containing benzylic bromine functionality. The base terpolymer isproduced by selective bromination of one of the benzylic hydrogens ofthe copolymer of an isoolefin having 4 to 7 carbon atoms and apara-alkylstyrene having the formula: ##STR2## in the presence ofbromine and a radical initiator so as to provide a brominated copolymerof isoolefin and para-alkylstyrene which copolymer includes thepara-alkylstyrene as: ##STR3## or as a mixture of (1) and (2), in whichR and R' are independently selected from hydrogen, alkyl, and theprimary and secondary alkyl halides, and in which the copolymer isotherwise substantially free of ring bromine or any bromine on thepolymer backbone chain. In accordance with one embodiment of theselective bromination process the radical initiator is light or heat. Inaccordance with another embodiment the radical initiator has a half-lifeof between about 5 and 2500 minutes, and preferably comprises a bis azocompound.

Substitution of radiation-reactive functional groups for the benzylicbromine which is a very active and versatile electrophile can beaccomplished by nucleophilic substitution reactions to introduce thedesired radiation-reactive functionality, and optionally, one or moreadditional functionalities.

The pendant radiation-reactive functionalized copolymers employed in thelithographic or corrosion barrier coating and/or method of the instantinvention can be characterized as a radiation-reactive, nucleophilicallysubstituted, halogenareal copolymer of an isoolefin andpara-alkylstyrene which copolymer includes the para-alkylstyrene as:##STR4## or as a mixture of (1), (2), and/or (3) and/or (4); wherein Rand R' are independently selected from the group consisting of hydrogen,alkyl, preferably C₁ to C₅ alkyl, and primary or secondary alkylhalides, preferably primary or secondary C₁ to C₅ alkyl halides; X isselected from the group consisting of chlorine and bromine, preferablybromine; Y represents a new radiation-reactive functional group orfunctional groups, preferably attached to the polymer via nucleophilicsubstitution of one of the benzylic halogens; and Z represents anoptional additional functional group or groups attached to the polymervia nucleophilic substitution of one of the benzylic halogens which maybe non-radiation reactive.

In accordance with a further embodiment of the present invention, amethod for making a lithographic, corrosion resistant or other coatingcomprises the steps of coating at least a portion of a surface of anarticle with a composition comprising radiation-reactive copolymerrecited above and exposing the coating to electromagnetic radiation toinduce crosslinking therein, The method may further comprise the stepsof forming an image of a pattern on the coating prior to the exposingstep to selectively block penetration of the radiation and removing anyuncrosslinked coating after the exposing step to reveal the image formedas crosslinked coating. The method may further comprise the step ofetching the surface of the article after the removing step wherein apattern mask is formed in the crosslinked coating.

In yet another embodiment of the present invention, aradiation-crosslinked coating composition comprises a crosslinkableradiation-reactive functionalized composition as recited above whereinat least a portion thereof is crosslinked by electromagnetic radiation.The crosslinked coating may be useful as printing elements and etchmasks or corrosion resistant, solvent resistant, shatterproofing andother type coatings.

Other embodiments of the present invention include various articlescomprising at least a portion thereof the radiation-crosslinked coatingcomposition of the present invention as recited above.

DETAILED DESCRIPTION OF THE INVENTION

The coating composition, preferably as a lithographic, corrosionresistant or sealant coating comprises anisobutylene/para-methylstyrene/para-bromomethylstyrene base terpolymer,functionalized with at least one radiation-reactive functional group.

A. Radiation-Reactive Copolymer

The coating comprises a radiation-reactive copolymer of an isoolefin andpara-alkylstyrene including the para-alkylstyrene as: ##STR5## wherein Wincludes at least Y, and may optionally include a mixture of Y and oneor more of hydrogen, X and Z, wherein R, R', X, Y and Z are as definedabove. The radiation-reactive substituted para-alkylstyrene (wherein Wis Y) may comprise from about 0.5 to about 55 percent by weight of thefunctionalized copolymer, preferably from about 0.5 to about 20 percentby weight, more Preferably from about 0.5 to about 15 percent by weight,and especially from about 1 to about 7 percent by weight of thecopolymer. The unsubstituted para-alkylstyrene (wherein W is hydrogen)may comprise from about 0.5 to about 90 weight percent of thefunctionalized copolymer, Preferably from about 1 to about 20 weightpercent and especially from about 2 to about 10 weight percent. Theradically halogenareal para-alkylstyrene (wherein W is X) may compriseup to about 55 percent by weight of the copolymer, preferably less thanabout 20 percent by weight, and more preferably less than about 15percent by weight of the copolymer. In a preferred embodiment,substantially complete conversion of the halogenated para-alkylstyreneis obtained, for example, by nucleophilic substitution thereof by Yand/or Z groups, so that the radiation-reactive copolymer is essentiallyfree of the halogenareal para-alkylstyrene preferably comprising lessthan about 1 percent by weight of the functionalized copolymer, morepreferably less than about 0.5 percent, most preferably less than about0.1 percent and especially less than about 0.02 mole percent.Functionalized Para-alkylstyrene (wherein W is Z) may be substitutedfrom 0 to about 55 percent by weight of the functionalized copolymer,preferably from 0 to about 20 percent, more Preferably from 0 to about15 percent by weight. The remainder of the radiation-reactive copolymergenerally comprises the isoolefin which usually ranges from about 10 toabout 99.5 weight percent of the radiation-reactive copolymer,preferably from about 80 to about 99 Percent by weight, more preferablyfrom about 90 to about 98 weight percent The M_(n) of the radiationreactive copolymer is from about 5000 to about 500,000, preferably fromabout 50,000 to about 300,000 and most preferably from about 50,000 toabout 150,000.

The radiation-reactive functionality may be derived from variouscompounds reactive by actinic or electron beam radiation. These comprisephotoinitiators from several different well known categories which canbe incorporated intoisobutylene/para-methylstyrene/para-bromomethylstyrene base terpolymerby means of nucleophilic substitution reactions between the benzylichalogen leaving group and the nucleophilic compound containing thephotoinitiator moiety. Representative photoinitiators include:

(a) aromatic aldehydes and ketones such as benzophenone,4-chlorobenzophenone, 4-hydroxybenzophenone, benzoquinone,naphthaquinone, anthraquinone, 2-chloroanthraquinone, benzylideneaceto-phenone, acetophenone, propiophenone, cyclopropyl phenyl ketone,benzaldehyde, β-napthylphenyl ketone, β-napthaldehyde, β-acetonaphthone,2,3-pentanedione, benzil, fluorenone, benzanthrone, Michler's ketone,bis(parahydroxybenzylidone) acetone, benzoin, deoxybenzoin,chlorodeoxybenzoin and the like;

(b) alkoxy and acyl substituted aromatic compounds such as2,2-dimethyloxy-2-phenyl, 1,3,5-triacetyl benzene, 2,5-diethoxystilbene,and the like;

(c) hetero aromatic compounds such as thioxanthone and the like;

(d) fused ring polycyclic aromatic compounds such as anthracene, pyreneand the like;

(e) N,N-disubstituted dithiocarbamates;

(f) conjugated unsaturated fatty acids such as tung oil acid andderivatives thereof;

(g) α,β-unsaturated aromatic carboxylic acids having the formula:##STR6## wherein R" is selected from the group consisting of H, CN, andNO₂ ; a and b are 0 or 1; and Ar is an aryl group such as, for example,phenyl, m-nitrophenyl, p-chlorophenyl, acetoxy phenyl, styryl, styrylphenyl, p-methoxyphenyl, 1-naphthyl, 2-naphthyl, 9-anthryl, 2-furfuryland 2-thienyl, and may be substituted by one or more additional groupssuch as, for example, hydrocarbyl, nitro, chloro, alkoxy, azide andsulfonazide (representative examples of these aromatic carboxylic acidsinclude benzoic acid, cinnamic acid, m-nitrocinnamic acid,p-chlorocinnamic acid, P-methoxycinnamic acid, chalcone acrylic acid,P-Phenylenebis(acrylic acid), p-azidobenzoic acid, p-sulfonazidobenzoicacid, α-cyanocinnamic acid, cinnamylideneacetic acid,cinnamylidene-malonic acid, α-cyanocinnamylideneacetic acid,β-(1)-naphthylacrylic acid, β-(2)-furfuryl-acrylic acid,α-cyano-β-(2)-thienylacrylic acid, β-(1)-naphthylacrylic acid,β-(9)-anthrylacrylic acid and esters and salts thereof, (e.g. sodiumbenzoate) and the like).

(h) nitro aromatic compounds such as, for example, picramide,nitronaphthalene, 5-nitroacenaphthlene, 2-nitrofluorene and the like;

(i) dye compounds such as rose bengal, acridine orange, chlorophyllin,crystal violet, eosin Y, fluorescein, flavin mononucleotide,hematoporphyrin, hemin, malachite green, methylene blue, rhodamine B,chlorophyll, cosine, erthrosin, methylene green, toluidine blue,thionine, and the like;

(j) azide-containing compounds such as azidobenzene, p-phenylenebisazide, p-azidobenzophenone, 4,4-diazidobenzophenone,4,4'-diazidodiphenylmethane, 4,4'-diazidostilbene, 4,4'-diazidochalcone,3,6-di(4'-azidobenzal)cyclohexanone,2,6-di(4'-azidobenzal)-4-methylcyclohexanone, and the like:

(k) diazonium salt radicals such as p-diazodiphenylamineparaformaldehydecondensates, 1-diazo-4-dimethylaminobenzene hydrofluoroborate,1-diazo-3-methyl-4-dimethylaniline sulfate and the like; and

(l) multifunctional compounds containing the above photosensitive groupssuch as 1,2-naphthoquinonediazide, 2,3,4-trihydroxybenzophenone,bis-(naphthoquinone-1,2-diazido-5-sulfonate),2-(naphthoquinone-1,2-diazido-5-sulfonyloxy)-3-hydroxynaphthalene,naphthoquinone-1,2-diazido-5-sulfonic acid novolak ester,naphthoquinone-1,2-diazido-5-sulfanilide, azidobenzoic acid,azidophthalic acid, and the like; and

(m) metal chelate compounds such as benzene chromium tricarbonyl and thelike,

A comprehensive discussion of photoinitiators is found in the Radekpublication mentioned earlier. These compounds generally either containsuitable reactive moieties for functionalization of the halogenarealisoolefin/para-alkylstyrene base terpolymers via nucleophilicsubstitution, or can be readily modified to incorporate suitablereactive moieties such as hydroxy or carboxyl radicals or carboxylatesalts or esters.

Coating performance as a lithographic or corrosion resistant filmdepends on the content and type of the radiation-reactive functionalizedcopolymer or copolymer blend, as well as the crosslink density.Crosslink density is a direct function of radiation exposure and thetype and concentration of radiation-sensitive functionality. Importantvariables in determining the type of functionality include the desireddegree of functionalization and wavelength of energy absorbance. Also,the photopolymer must generally exhibit good crosslinking response whenirradiated in the presence of any additional components contained in thecoating composition including any additives and/or extenders.

The cinnamate derivative photopolymer, for example, absorbs high levelsof irradiated energy because of its strong absorbance. Consequently,coating systems incorporating cinnamates as a UV-reactive functionalitygenerally require higher doses of UV radiation and have shallowercrosslink depths. These systems work best with thin coatings, and areparticularly desirable in applications wherein crosslinking is to berestricted to an outer layer or shell exposed to the UV radiation.Coatings incorporating benzophenone on the other hand do not absorb asmuch UV energy because of its weaker absorbances, and they have highhydrogen abstraction reactivity from the photoexcited state.Consequently, coating systems including benzophenone require reduced UVradiation doses and have greater crosslink depth.

Selection of the type of functional group also involves considering theradiation wavelength to be employed to excite the functional group.Among those which are reactive to UV wavelengths include cinnamates,benzophenones, thioxanthones, anthraquinones, dithiocarbamates, and thelike. On the other hand, naphthoquinone-derivatized photopolymers, forexample, are sensitive to visible light, while tung oil acid derivativesare an example of a polymer crosslinkable by high energy radiation suchas gamma and electron beam radiation.

Coating performance, e.g., adhesion to various substrates, is alsodependent upon composition of the polymer backbone, including themolecular weight, architecture and concentration of para-methylstyrene,i.e., the degree to which the radiation-reactive polymer iselastomeric-like (high in isobutylene, low T_(g)) versus the degree towhich it is thermoplastic-like (higher in para-methylstyrene, highT_(g)). Increasing para-methylstyrene concentration in the polymerbackbone generally contributes to an overall increase in T_(g), andconsequently, is a variable for optimization.

Likewise related is optimization of molecular architecture, i.e.branched versus linear molecules. Incorporation of other functionalityinto radiation curable coating systems opens new variables for evengreater control of polymeric architecture and property optimization fora variety of different substrates.

The paths taken by radiation-reactive crosslinking depend on the type offunctionality incorporated. For example, the cinnamate derivativecopolymer, e.g. cinnamoyl (φCH═CH--C(O)--), undergoes 2+2photocycloaddition upon UV initiation: ##STR7##

On the other hand, the benzoylbenzoate derivative undergoes free radicalcrosslinking under UV exposure. The incorporated benzophenone moiety isa well known photoinitiator in that it reacts with UV radiation toproduce a free radical in the enchained benzophenone functionality via ahydrogen abstraction mechanism.

The N,N-disubstituted dithiocarbamate derivative also undergoes radicalcrosslinking upon UV exposure. Crosslinking is attributed to the readyability of the dithiocarbamate ester functionality to form stableradicals under irradiation to permit radical crosslinking and otherradical chemistry reactions to occur, rather than backbone cleavage asnormally occurs with isobutylene based polymers.

Tung oil fatty acid is a fatty acid high in eleostearic acid derivedfrom tung oil and containing conjugated unsaturations. Exposure toelectron beam irradiation initiates crosslinking in the tung oil esterfunctionalized copolymer.

The anthraquinone-2-carboxylate ester functionalized copolymer containsthe photoinitiator anthraquinone. UV irradiation initiates radicalcrosslinking.

The presence of other functionality is optional and may be eitherinterdispersed on a single functionalized base copolymer with multiplefunctional groups (of which at least one is radiation-reactive), or twoor more functionalized copolymers may be blended together. The presenceof the additional functionality enables other desirable properties to beincorporated into a coating system. For example, the presence of aminefunctionality in addition to radiation-curable functionality canfacilitate emulsification application of radiation-curable lithographiccoatings. Also, the amine derivatives can be used in combination withthe benzophenone photoinitiation to provide easily abstracted protons.

As another example of mixed functionality, certain radiation-reactivefunctional groups act as energy amplifiers and transfer agents for otherradiation-reactive groups, thereby allowing for enhanced sensitivity ofselected coatings with lower energy absorbance in a wider frequencyrange. Photoexcitable acroleinium salt functionality present in acoating composition can act as an energy amplification and transferagent for cinnamate groups which otherwise have a high UV absorbance,low UV transmissivity, and a narrow UV frequency photoinitiation range.The addition of the photoexcitable functionality can allow for greatercuring depth and/or thicker coatings in a cinnamate-based system.

The radiation-reactive copolymer includes at least oneradiation-reactive functionality so the coating composition is curableby electromagnetic radiation. By incorporating the photoinitiatordirectly onto the pendant para-methylstyrene groups randomly dispersedin the polyisobutylene backbone, the polymer can be cured directly byelectromagnetic radiation. Furthermore, radiation-curable systemscontaining a single derivatized copolymer or a blend of severalcopolymers with at least a single radiation-curable functionality andother functional groups can be tailored lithographic or corrosionbarrier systems containing specific functional groups to enhanceadhesion to specific substrates, both polar and non-polar categories.For example, the presence of carboxylic acid functionality can enhancealuminum adhesion whereas silane functionality enhances adhesion toglass. In addition, silane functionality may be useful in semiconductormanufacturing processes requiring organosilicon polymer photoresistcoatings, i.e. multilayer lithography.

It is understood that the above illustrative examples should not beconsidered limiting as one having ordinary skill in the art candetermine embodiments of systems for lithographic or corrosion barriercoatings with useful multiple functional groups incorporated thereinother than the ones described above.

B. Other Resin Components

An optional component of the lithographic or corrosion resistant coatingcompositions of the present invention is a tackifier suitable for usewith UV- or EB-reactive copolymers. Suitable tackifiers include thoseresins which are compatible with the copolymer or copolymer blend.Tackifiers are chosen to impart substantial adhesive strength, promotesubstrate wetting and generally enhance coating performance, e.g.,optimize tack performance versus temperature performance of the curedcomposition where applicable. The tackifier must generally notsubstantially interfere with the photosensitivity of the UV- orEB-reactive polymer(s) and the ability for gel conversion.

Tackifier components suitable for use in this invention includealiphatic and aromatic hydrocarbon resins such as ESCOREZ or WINGTACK95. WINGTACK 95 is the tradename for a diene-olefin copolymer ofpiperylene and 2-methyl-2-butene having a softening point of 95° C. Theresin is prepared by the cationic polymerization of 60 weight percentpiperylene, 10 weight percent isoprene, 5 weight percentcyclopentadiene, 15 weight percent 2-methylbutene and about 10 weightpercent dimer. See U.S. Pat. No. 3,577,398. Other tackifying resins ofthe same general type may be employed in which the resinous copolymercomprises 20-80 weight percent of piperylene and 80-20 weight percent of2-methyl-2-butene. Other adhesion-promoting resins which are also usefulin the compositions of this invention include hydrogenareal rosins,rosin esters, polyterpenes, terpenephenol resins, and polymerized mixedolefins. Hydrogenareal hydrocarbon resins obtained under the tradedesignation ESCOREZ 5380 and ECR-143H are preferred because unsaturationpresent in the tackifier may reduce the conversion of polymer to gelthrough radiation energy absorption or through tackifier participationin crosslinking when the coating is cured. These tackifiers typicallyhave a ring and ball softening point from about 10° C. to about 180° C.,preferably from about 15° C. to about 75° C. Other hydrocarbontackifiers obtained from Exxon Chemical Co. under the trade designationsECR-111, and ECR-327 have also been found to be particularly preferred.ECR-143H resin, for example, is prepared by the cationic polymerizationof a C₅ olefin/diolefin feed stream as described in U.S. Pat. No.4,916,192 which is hereby incorporated by reference herein.

PSA properties are dependent on selection of tackifier resin.Particularly important is the T_(g) of the tackifier. Optimizationstudies show that tack-related properties which are nominally inverselyproportional to crosslink density can be improved by optimizing theT_(g) of the PSA system. Selection of tackifier is an important variablein this regard. For example, when ECR-143H and ECR-111 tackifiers wereblended together in equal proportions, several tack properties improvedin PSA system incorporating the blended tackifier over PSA systemsincorporating each individual tackifier resin. General tackifiercomposition is also a strong variable in PSA property optimization. Thepresence of aromaticity is beneficial for compatibility.

An additional optional component of the coating composition of thepresent invention is a radiation inactive polymer wherein such additiondoes not interfere with the necessary radiation sensitivity. Radiationinactive resins may act as low cost extenders or introduce other desiredfunctionality.

C. Preparation and Utility of the Coating Composition

Coating systems which are an embodiment of this invention may optionallycontain a non-radiation-reactive resin including both tackifiers andhigh polymers blended up to about 50 parts by weight and thefunctionalized polymer having at least one radiation-reactive functionalgroup in an amount of 50 parts by weight or more wherein the parts byweight of the radiation- and non-radiation-reactive components total100.

Other additives may include antioxidants, non-polymeric organic orinorganic particulated fillers or reinforcing agents, coupling agents,dyes and pigments, and the like which do not appreciably obstruct theradiation crosslinking.

The antioxidant or stabilizer can be added at from about 0.1 to about 3percent by weight, preferably from about 0.1 to about 1.5 percent byweight, more preferably from about 0.1 to about 1 percent by weight, andtypically at about 0.5 weight percent.

Particulated fillers which may be also used for thickening and pricereduction include glass, silica, amorphous SiO₂, fumed alumina, calciumcarbonate, fibers and the like. Suitable commercially available fillersare available under the trade designations CAB-0-SIL, ZEOSIL 35, AEROSILR972, DUCRAL 10 and the like.

Suitable coupling agents include (but are not limited to) organometalliccompounds such as, for example, silane-based compounds, organotitanates,organozirconates, organozircoaluminates, chrome complexes and the like.These are generally selected to promote adhesion based on the substratesand/or fillers involved in the particular application.

Suitable dyes include Fuchsine (CI 42510), Calcocid Green S (CI 44090),Solvent Yellow 34 (CI 4100B), and the like. Suitable pigments includetitanium dioxide, colloidal carbon, graphite, ceramics, clays, phosphorparticles and metal particles, e.g. aluminum magnetic iron, copper, andthe like.

The coating compositions of this invention are preferably prepared asorganic solvent solutions of the radiation-reactive copolymer and anyother components, although copolymer emulsions and hot melts may also beused if so desired. The coating compositions may be applied to thesubstrate from a solution of up to about 40 percent weight solids of theingredients in a solvent such as toluene, the solvent being removed byevaporation prior to crosslinking by exposure to the radiation.Alternatively, the ingredients may be mixed in a solvent, the mixturemay be emulsified and the solvent evaporated, and the coating may beapplied to a substrate as 50-60 percent weight solids emulsion, thewater being removed by evaporation with conventional drying equipmentand techniques prior to crosslinking.

For hot melt application, the coating compositions may be prepared byblending the radiation-reactive polymer with any optional component inthe melt until a homogeneous blend is obtained. Various methods ofblending materials of this type are known to the art, and any methodthat produces a homogeneous blend is satisfactory. Typical blendingequipment includes, for example, mixing extruders, roll mills, Banburymixers, Brabenders and the like. In general, the blend components blendeasily in the melt and a heated vessel equipped with a stirrer is allthat is required. The components are added in no particular order, butgenerally the polymer resin is added first and heated in the vesseluntil molten. Thereafter, any optional components are then added.

The hot melt formulation may be cooled and later reheated for use, orused directly, e.g. supplied from a reservoir or melt pot to a substrateusing conventional equipment, for example, for pumping or pressureextrusion through slot dies. An important feature of the presentinvention is that the hot melt formulation has a good melt pot stabilityso that appreciable premature curing of the formulation is not usuallyencountered at typical hot melt conditions, such as, for example, fromabout 60° C. to about 140° C. Generally, the hot melt is heatedsufficiently for a target viscosity of about 100,000 cps, although aviscosity as high as 150,000 cps can usually be tolerated. For suitablepot stability, the viscosity of the hot melt should not increase morethan 20 percent when maintained at the pot temperature for a period of 8hours.

The preparation of coated articles such as films, sheets, plates andmolded objects involves the initial step of coating at least a portionof a surface of the selected article with a solution, emulsion or hotmelt of the radiation-reactive composition. Any suitable coatingtechnique may be employed while applicable substrates, includingcomposites thereof, may be comprised of paper and paperboard;fiberglass; wood; graphite; conductive metals, e.g. copper, aluminum,zinc, and steel, etc.; and semi-conductive substrates such as siliconand gallium arsenide; glass and ceramic; textiles, both natural andsynthetic, woven and non-woven; synthetic resins including the homo- andcopolymers of ethylene, propylene, vinyl chloride, vinylidene chloride,vinyl acetate, styrene, isobutylene, and acrylonitrile; polyvinylacetal; polyethylene terephthalate; polyamides and, cellulose esterssuch as cellulose acetate and cellulose butyrate. The latter polymericsubstrates may contain fillers or reinforcing agents such as the varioussynthetic, natural or modified fibers such, for example as cellulosicfiber, e.g. cotton, cellulose acetate, viscose rayon, and paper; glass;and, polyamide fibers. These reinforced substrates may be issued inlaminated or composite form.

The coating of the radiation-reactive copolymer composition should beapplied to the substrate surface so that upon drying its thickness willbe in the range of about 0.05 to about 10 mils. Drying of the wetpolymer coating may be achieved by air drying or by the application ofany other particular drying technique whose use is favored by thepractitioner. The substrate comprising the radiation-reactive coatingmay be stored for Prolonged periods before its ultimate utilization.

Suitable sources of actinic radiation employed to effect thecrosslinking reaction include carbon arc, mercury-vapor arc andfluorescent sun lamps. The electron beam radiation or high energyionizing radiation can be obtained from any suitable source such as anatomic pile, a resonant transformer accelerator, a Van de Graaf electronaccelerator, a Linac electron accelerator, a betatron, a synchrotron, acyclotron, or the like. Radiation from these sources will produceionizing radiation such as electrons, protons, neutrons deuterons, gammarays, x-rays, α-particles and β-particles.

The crosslinking reaction is conveniently effected at room temperature,but it can be conducted at depressed or elevated temperatures ifdesired. It is also within the spirit and scope of the invention toeffect the crosslinking reaction within the confines of an inertatmosphere to prevent air inhibition of the crosslinking reaction and toprevent oxidative degradation of the polymer. The amount and kind ofradiation required depends primarily on the type and amount ofradiation-sensitive functionality employed, thickness of the coating andthe level of curing desired. Suitable doses of EB radiation include fromabout 0.2 megarad to about 20 megarad, preferably from about 1 megaradto about 10 megarad. Suitable doses of UV radiation include from about0.05 to about 2 J/cm², preferably from about 0.1 to about 1 J/cm².

The resulting crosslinkable compositions can be used for a wide varietyof applications including lithographic, corrosion resistant, barrier andother applications where high oil, grease and solvent resistance as wellas increased stiffness resulting from a crosslinked matrix are required.Specifically, they may be used in photo-reproduction processes such asin photography, photomechanical reproductions, lithography and intaglioprinting; in processes requiring photo-etch-resist masks wherein it isdesirable to engrave or etch intricate shapes and/or designs such asmicrocircuit designs without the use of cutting tools; as corrosionbarrier films on metals; as water, oil and/or solvent-proofing of coatedarticles including, paper, cardboard, textiles, plastics, elastics;shatterproofing coatings on glass; caulks and sealants; and the like.

Lithography generally refers to processes for pattern transfer betweenvarious media. A lithographic coating is generally aradiation-sensitized coating suitable for receiving a projected image ofthe subject pattern. Once projected, the image is indelibly formed inthe coating. The projected image may either be a negative or positive ofthe subject pattern. Typically, a "transparency" of the pattern is madehaving areas which are selectively transparent or opaque to the"projecting" radiation. Exposure of the coating through the transparencycauses the image area to become selectively crosslinked and consequentlyeither more or less soluble (depending on the coating) in a particularsolvent developer. The more soluble, i.e. uncrosslinked, areas areremoved in the developing process to leave the pattern image in thecoating as less soluble crosslinked polymer.

Suitable developing solvents include perchloroethylene, methylenechloride, ethylene dichloride, methyl ethyl ketone, n-propanol, toluene,benzene, ethyl acetate and water, where applicable. The solvent liquidused for this operation must be selected with care since it should havegood solvent action on the unexposed areas, yet have little action uponeither the insolubilized copolymer or the substrate. The developingsolvent should be allowed to remain in contact with the coating for aperiod of from about 30 seconds to 3 minutes depending upon theparticular solvent being utilized. The thus developed polymer coatingshould next be rinsed with fresh solvent and thereupon dried.

The developing process, particularly in printing applications, may alsocomprise several different steps including etching of an underlyingsubstrate to enhance the height of the relief image area, removing theuncrosslinked coating and altering the hydrophilic properties of thesubstrate.

The present invention has utility in photo-reproduction processes wherethe crosslinked coating remains as raised printing elements generally ona plate. Ink may be carried by the raised portion of the plate as indry-offset printing and ordinary letterpress printing, or may be carriedby the recessed portions of the plate such as in intaglio printing, e.g.line and inverted halftone. Thickness of the radiation-reactive layer isa direct function of the thickness desired in the relief image and thiswill depend on the subject being reproduced and particularly on theextent of the non-printing areas. Further examples of such uses areoffset printing, silk screen printing, duplicating pads, manifoldstencil sheeting coatings, lithographic plates, relief plates, gravureplates, photoengraving, collotype and planographic type elements,magenta screens, screen stencils, dyeable images of the halftone andcontinuous type, in direct positive and negative systems utilizing wetdevelopment which incorporate color formers and coupling agents in vapordeveloped systems which incorporate diazonium salts and coupling agents.

In making a negative surface plate, the coated plate is placed in avacuum printing frame and the negative positioned accurately over it.The frame is closed and a vacuum applied to pull the negative into closecontact with the plate for exposure to a powerful light source forexample. The light passes through the clear areas of the negative toharden the plate coating, and the plate is removed from the frame andthe image is developed.

In producing deep-etch lithoplates, the coating is exposed to lightthrough a positive. The unhardened areas are washed away, but in thiscase the function of the hardened areas is not to act as the lithoplatebut to form a protective stencil while the image areas are lightlyetched and then filled with a hard lacquer.

Bimetal plates take advantage of the fact that oil and water do not wetall metals with the same ease. An oleophilic metal, such as copper, isused for the image and hydrophilic metal, for example chromium, for thenonimage areas. The method of platemaking is similar to that used in thedeep-etch process but the purpose of etching is to remove a thin layerof chromium to leave bare copper exposed to form the image.

These lithographic coating compositions are also useful as resist layers(i.e. photoresists) in carrying out chemical and other type etching orengraving operations. Following pattern transfer and removal of theuncrosslinked coating, the crosslinked coating comprises a mask for theetching step. Applications include the preparation of ornamental plaquesor for producing ornamental effects; as patterns for automatic engravingmachines, foundry molds, cutting and stamping dies, name stamps, reliefmaps for braille, as rapid cure coatings, e.g. on film base; astelevision phosphor photobinders, as variable area sound tracks on film;for embossing plates, paper, e.g. with a die prepared from theradiation-sensitive coating; particularly as photoresists in themanufacture of printed circuits, other plastic articles and microchips.

In semiconductor manufacturing processes, for example, the exposed anddeveloped resist becomes a pattern mask for anisotropic etching of anunderlying layer and/or semiconductor substrate. The etching istypically carried out by chemical or plasma means to which the mask isinert. The steps of exposing and developing the resist layer with asuitable pattern is similar to the method described earlier forproducing printing elements. Following anisotropic etching, the resistlayer may be removed by an isotropic plasma or chemical etch to whichthe mask polymer is not inert.

The radiation-curable coating compositions of the present invention canreadily be shaped into films, sheets, and other molded articles and thenexposed to active radiation, such as visible, ultraviolet, or highenergy radiation, to crosslink the polymers and thereby render theminfusible and insoluble for use as corrosion resistant, solventresistant and other barrier coatings.

The present coating composition may be used as a corrosion resistantbarrier coating on various metal surfaces in intimate contact withcorrosion-causing fluids or gases including water, seawater, high andlow pH fluids, and the like or exposed to a corrosion-causingenvironment. Examples include, liners in food and beverage containers;liners in vessels, pipes, and miscellaneous equipment used manufacturingplants, ships, and the like; and anti-rust coatings for automobiles,etc.

As other useful coatings, the uncrosslinked copolymers may be used asfilm-forming binders or adhesives in the production of various coatingand/or impregnating compositions for application to papers and textileswhich after irradiation can be rendered resistant to removal by heatingor solvents. The copolymers can be used as binders for non-woven fabricsor webs. They may be applied uniformly over the entire area of thenon-woven web or in any predetermined pattern, e.g. along intersectingsets of parallel lines, either straight or curved in a regular or evensomewhat irregular array. The impregnated non-woven web may then besubjected to actinic radiation, for example, to crosslink the polymerwherever it is present, thereby rendering the treated non-woven web moreor less resistant to disintegration by water or solvents.

As a web coating the present invention may be applied uniformlythroughout the area of the web and then the web may be crosslinked in apredetermined pattern through a light filter or opaque screen so thatonly selected areas of the polymer film coating are effected. After thescreened exposure, the unexposed portions of the coating may be removed.

In such methods, the coatings of the present invention may be used toproduce "wet wipes", disposable diapers and/or diaper covercloths. Theuse of a screen of filter can control the extent of crosslinkingselectively in various areas of the bonded diaper or diaper coverclothso that, for example, the crotch areas can be rendered resistant todisintegration by water-soaking whereas the peripheral area can bedisintegrated within a short time of half a minute to two minutes or soon soaking in water.

In addition, the coating compositions of the present invention may beapplied as sealants and caulks at low viscosity and cured by exposure toUV or EB radiation and as protective shatter-proofing coatings for glassand other articles comprising brittle materials.

D. Preparation of the Radiation-Reactive Copolymer

1. Copolymer Precursor Preparation

This invention is, in part, based upon the discovery that thepolymerization of isoolefin and para-alkylstyrene under certain specificpolymerization conditions now permits one to produceradiation-functionalizable (via halogenation and nucleophilicsubstitution) precursor copolymers which comprise the direct reactionproduct (that is, in their as-polymerized form), and which haveunexpectedly homogeneous uniform compositional distributions. Thus, byutilizing the polymerization procedures set forth herein, the polymericbackbones, or precursor copolymers of the novel functionalizedcopolymers employed in the coating compositions of the present inventioncan be produced. These copolymers, including the radiation-reactivecopolymers, as evaluated by gel permeation chromatography (GPC),demonstrate narrow molecular weight distributions and substantiallyhomogeneous compositional distributions, or compositional uniformityover the entire range of compositions thereof. Put another way, at leastabout 95 percent by weight of the precursor copolymer product has apara-alkylstyrene content within about 10 percent by weight, andpreferably within about 7 percent by weight, of the averagepara-alkylstyrene content for the overall composition, and preferably atleast about 97 percent by weight of the copolymer product has apara-alkylstyrene content within about 10 percent by weight, andpreferably within about 7 percent by weight, of the averagepara-alkylstyrene content for the overall composition. In a mostpreferred embodiment hereof, this is demonstrated by the fact that thenormalized differential refractive index (DRI) and ultraviolet (UV)curves obtained by GPC for these functionalized copolymers areessentially superimposeable on each other and substantially merge into asingle curve in most instances. This substantially homogeneouscompositional uniformity thus particularly relates to theintercompositional distribution. That is, with the precursor copolymersof this invention, as between any selected molecular weight fraction thepercentage of para-alkylstyrene therein, or the ratio ofpara-alkylstyrene to isoolefin, will be substantially the same, in themanner set forth above. Since the relative reactivity ofpara-alkylstyrene with isoolefin such as isobutene is close to 1.0, theintracompositional distribution of these copolymers will also besubstantially homogeneous. That is, these precursor copolymers areessentially random copolymers, and in any particular polymer chain thepara-alkylstyrene and isoolefin units will be essentially randomlydistributed throughout that chain.

The properties of these precursor copolymers leads to a number ofdistinct advantages over the prior art, including the ability to produceuseful functionalized copolymers having number average molecular weightsgenerally greater than about 5000. The precursor copolymers useful forradiation-reactive functionalization in the coatings, methods andarticles of the present invention include compositionally homogeneouscopolymers having number average molecular weight (M.) from about 5000to about 500,000, preferably from about 50,000 to about 300,000, morepreferably from about 50,000 to about 150,000. These products alsoexhibit a relatively narrow molecular weight distribution. Inparticular, these functionalized copolymers thus exhibit M_(w) /M_(n)values of less than about 6, preferably less than about 4, morepreferably less than about 2.5 and at the same time, depending Upon theultimate intended use thereof.

Thus, distributed throughout the precursor copolymer are thepara-methylstyrene units: ##STR8## in which R and R' are, independently,selected from the group consisting of hydrogen, alkyl, preferably C₁ toC₅ alkyl, and primary and secondary alkyl halides, preferably primaryand secondary C₁ to C₅ alkyl halides.

With respect to the ratio of the monomers employed to produce theprecursor copolymers for nucleophilic functionalization into radiationsensitive copolymers, it is a distinct advantage of the presentinvention that a very wide range of the ratio of the monomers in theprecursor copolymer product can be utilized in accordance with thisinvention. It is therefore possible, for example, to produce precursorcopolymer products which operably comprise from about 10 to about 99.5percent by weight, preferably between about 80 and 99 percent by weight,and most preferably from about 90 to about 98 percent by weight of theof the isoolefin or isobutylene and from about 0.5 to about 90 percentby weight, preferably from about 1 to about 20 percent by weight, morepreferably from about 2 to about 10 percent by weight of thepara-alkylstyrene, preferably para-methylstyrene. On the other hand, itis also possible to produce thermoplastic materials comprising higherconcentrations of para-alkylstyrene, and therefore the copolymerscomprise from about 10 to about 99.5 percent by weight of the isoolefin,preferably isobutylene, and from about 0.5 to about 90 percent byweight, preferably from about 1 to about 90 percent by weight of thepara-alkylstyrene, or preferably para-methylstyrene.

Isobutene and para-methylstyrene are readily copolymerized undercationic conditions. The polymerization can be carried out by means of aLewis acid catalyst. Suitable Lewis acid catalysts (includingFriedel-Crafts catalysts) include those which show good polymerizationactivity with a minimum tendency to promote alkylation transfer and sidereactions which can lead to branching and the production of crosslinksresulting in gel-containing polymers with inferior properties. Thepreferred catalysts are Lawis acids based on metals from Group IIIa, IVand V of the periodic table of the elements, including boron, aluminum,gallium, indium, titanium, zirconiota, tin, vanadium, arsenic, antimony,and bismuth. The Group IIIa Lawis acids have the general formula R_(m)MX_(n), wherein M is a Group IIIa metal, R is a monovalent hydrocarbonradical selected from the group consisting of C₁ to C₁₂ alkyl, aryl,alkylaryl, arylalkyl and cycloalkyl radicals; m is a number from 0 to 3;X is a halogen independently selected from the group consisting offluorine, chlorine, bromine, and iodine; and the sum of m and n is equalto 3. Nonlimiting examples include aluminum chloride, aluminum bromide,boron trifluoride, boron trichloride, ethyl aluminum dichloride(EtAlCl₂), diethyl aluminum chloride (Et₂ AlCl), ethyl aluminumsesquichloride (Et₁.5 AlCl₁.5), trimethyl aluminum, and triethylaluminum. The Group IV Lawis acids have the general formula MX₄, whereinM is a Group IV metal and X is a ligand, preferably a halogen.Nonlimiting examples include titanium tetrachloride, zirconiumtetrachloride, or tin tetrachloride. The Group V Lawis acids have thegeneral formula MX_(y), wherein M is a Group V metal, X is a ligand,preferably a halogen, and y is an integer from 3 to 5. Nonlimitingexamples include vanadium tetrachloride and antimony pentafluoride.

The preferred Lawis acid catalysts may be used singly or in combinationwith co-catalysts Such as Brensted acids, such as anhydrous HF or HCl,or alkyl halides, such as benzyl chloride or tertiary butyl chloride. Inparticular, the most preferred catalysts are those which can beclassified as the weaker alkylation catalysts, and these are thus theweaker Lewis acids from among the catalysts set forth above. These mostpreferred catalysts, such as ethyl aluminum dichloride, and preferablymixtures of ethyl aluminum dichloride with diethyl aluminium chloride,are not the catalysts that are normally preferred for use inconventional alkylation reactions, since again in the present case thereis a strong desire to minimize side reactions, such as the indenyl ringformation which would be more likely to occur with those catalystsnormally used to promote conventional alkylation reactions. The amountof such catalysts employed will depend on the desired molecular weightand the desired molecular weight distribution of the copolymer beingproduced, but will generally range from about 20 ppm to about 1 percentby weight, and preferably from about 0.001 to about 0.2 percent byweight, based upon the total amount of monomer to be polymerizedtherein.

Suitable diluents for the monomers, catalyst components and polymericreaction products include the general group of aliphatic and aromatichydrocarbons, used singly or in admixture, and C₁ to C₄ halogenatedhydrocarbons used in admixture with hydrocarbon diluents in an amount upto about 100 percent by volume of the total diluent fed to the reactionzone. Typically, when the monomers are soluble in the selected diluent,the catalyst may not necessarily also be soluble therein.

The process can be carried out in the form of a slurry of polymer formedin the diluents employed, or as a homogeneous solution process. The useof a slurry process is, however, preferred, since lower viscositymixtures are produced in the reactor, and slurry concentrations of up toabout 40. percent by weight of polymer are possible. At higher slurryconcentrations it is possible to operate a more efficient process inwhich it is necessary to recycle less of the reactants and diluent foreach unit of polymer produced. For instance, at 33 percent slurryconcentration it is only necessary to recycle two units of unreactedreactants and diluent for each unit of polymer. In any event, the amountof diluent fed to the reaction zone should be sufficient to maintain theconcentration of polymer in the effluent leaving the reaction zone belowabout 60 percent by weight, and preferably in the range from about 5 toabout 35 percent by weight, depending upon the process being used andthe molecular weight of polymer being produced. Too high a concentrationof polymer is generally undesirable for several reasons, including poortemperature control, rapid reactor fouling, and the production of gel.Polymer concentrations which are too high will raise the viscosity inthe reactor and require excessive power input to insure adequate mixingand the maintenance of effective heat transfer. Such inadequate mixingand loss of heat transfer efficiency can thus result in localized highmonomer concentrations and hot spots in the reactor which can in turncause fouling of reactor surfaces. However, the prior art tendency forgel production at higher polymer concentrations when producingdiene-functional butyl rubbers (e.g., isobutene-isoprene copolymer) issubstantially eliminated in accordance with the present process withpara-methylstyrone as the functional comonomer. In any event, typicalexamples of the diluents which may be used alone or in admixture includepropane, butane, pentans, cyclopentane, hexane, toluene, heptane,isooctane, etc., and various halohydrocarbon solvents which areparticularly advantageous herein, including methylene chloride,chloroform, carbon tetrachloride, methyl chloride, with methyl chloridebeing particularly preferred.

It should also be noted that, with any particular monomers (for example,isobutene and para-methylstyrene), as the compositional distribution ofthe feed is altered therebetween, in order to maintain either a slurryor solution polymerization it can be necessary to change the diluentsemployed, depending upon the effect on the solubility of the copolymerin the diluent as the ratio of the monomers utilized therein is altered.In any event, as noted above, an important element in making thecopolymer precursor of the present invention is the exclusion ofimpurities from the polymerization reactor, namely impurities which, ifpresent, will result in complexing with the catalyst or copolymerizationwith the isoolefin or the para-alkylstyrene, which, in turn, willprevent one from obtaining the molecular weight properties necessary formaking the pre-functionalized copolymer reactant and obtaining improvedphysical properties of the PSA or coating product of this invention.Instead, polymers which do not have the substantially homogeneouscompositional distributions and/or narrow molecular weight distributionsof the present invention, will be produced.

Most particularly, these impurities include catalyst poisoningmaterials, moisture, and other copolymerizable monomers, such as, forexample, meta-alkylstyrenes and the like. These impurities should bekept out of the system so that, in turn, the para-alkylstyrene is atleast about 95.0 percent by weight pure, preferably at least about 97.5percent by weight pure, and the isoolefin is at least about 99.5 percentby weight pure, and preferably at least about 99.8 percent by weightpure. The diluents employed therein should be at least about 99.0percent by weight pure, and preferably at least about 99.8 percent byweight pure.

In general, the polymerization reactions are carried out by admixing thepara-methylstyrene and isobutene in the presence of the catalyst (suchas a Lewis acid catalyst) and diluent in a copolymerization reactor,with thorough mixing, and under copolymerization conditions, includingtemperatures less than about 0° C., in the case of lower molecularweight polymers, and providing a means of removing the heat ofpolymerization in order to maintain a desired reactor temperature. Inparticular, the polymerization may be carried out under batch conditionsof cationic polymerization, such as in an inert gas atmosphere and thesubstantial absence of moisture. Preferably, the polymerization iscarried out continuously in a typical continuous polymerization processusing a baffled tank-type reactor fitted with an efficient agitationmeans, such as a turbo-mixer or propeller, and draft-tube, externalcooling jacket and internal cooling coils or other means of removing theheat of polymerization, inlet pipes for monomers, catalysts anddiluents, temperature sensing means and an effluent overflow to aholding drum or quench tank. The reactor must be purged of air andmoisture and charged with dry, purified solvent or a mixture of solventsprior to introducing monomers and catalyst.

Reactors which are typically used in butyl rubber polymerizations aregenerally suitable for use in the polymerization reactions of thepresent invention copolymer intermediate. These reactors are basicallylarge heat exchangers in which the reactor contents are rapidlycirculated through rows of heat exchange tubes which are surrounded byboiling ethylene so as to remove the heat of polymerization, and thenthrough a central draft tube by means of an efficient marine-typeimpeller. Catalyst and monomers are introduced continuously into thereactor and mixed by the pump, and reactor effluent then overflows intoa steam-heated flash tank. Heat of polymerization can also be removed bya pump-around loop in which the reactor contents are continuouslycirculated through an external heat exchanger in the loop.

When conducting a slurry polymerization process, the reactor isgenerally maintained at temperatures of from about -85° C. to about-115° C., and preferably from about -89° C. to about -96° C. Solutionpolymerizations and cement suspension polymerizations can be run at muchwarmer temperatures, such as about -40° C., depending on the copolymermolecular weight desired and the particular catalyst system used.Therefore, an acceptable solution polymerization temperature range isfrom about -35° C. to about -100° C., and preferably from about -40° C.to about -80° C.

The overall residence time can vary, depending upon, e. g., catalystactivity and concentration, monomer concentration, reaction temperature,and desired molecular weight, and generally will be from about oneminute to about five hours, and preferably from about 10 to about 60minutes.

Since the reactor gradually fouls with polymer in the slurrypolymerization process, however, it generally becomes necessary toperiodically remove the reactor from production for cleaning. It is thusmost important that the fouling polymer be soluble, so that the reactorcan be cleaned by solvent washing and then returned to service. Anydeposition of insoluble gel polymer in the reactor would beunacceptable, since it would render solvent washing ineffective, andnecessitate the use of elaborate and expensive reactor cleaningprocedures. This necessity to avoid the deposition of a polymer gel inthe reactor is typically one of the limitations on the amount of dienewhich can be used in making butyl rubbers (e.g., isobutylene-isoprenecopolymer).

The para-methylstyrene/isobutene copolymers of this invention alsoafford significant advantages when produced using a solutionpolymerization process. Since para-methylstyrene does not cause thesevere molecular weight depression characteristic of dienes, and sincethe molecular weight versus polymerization temperature response of thesenew copolymers is much flatter than with diene functional butylcopolymers, high molecular weight copolymers can be made at much warmertemperatures (i.e., about -40° C. versus less than about -90° C. withthe diene functional butyl copolymers). These warmer polymerizationtemperatures translate into a much lower viscosity at any given polymerconcentration and molecular weight. In particular, it is now possible toConduct these solution polymerizations at temperatures of from about-35° C. to about -100° C., and preferably from about -40° C. to about-80° C. When producing the low molecular weight polymers of thisinvention, for example, M_(n) of less than 25,000, temperatures as warmas 0° C. can be used, or even up to about +10° C. for very low molecularweight polymers with M_(n) in the range of about 500 to 1,000.Furthermore, the para-methyl styrene/isobutene copolymers have a muchnarrower molecular weight distribution than do the diene functionalbutyl rubbers, and this also results in a much lower solution viscosityat a given number average molecular weight.

Solution polymerization has the further advantage, particularly with thepara-methylstyrene/isobutene copolymers of this invention, in that theprecursor copolymers are produced in a desirable solution state in whichpost-polymerization chemical modification can be conducted. It is alsopossible to halogenate and graft nucleophile moieties onto the precursorpolymer in the bulk state (i.e., using an internal mixer, extruder,etc.), but most reactions can be more easily performed in a morecontrolled manner on polymer solutions, which afford better mixing, heattransfer, removal of unwanted by-products, etc.

The polymerization processes can also be carried out in the form of aso-called "cement suspension" polymerization process. In particular,these are polymerization reactions carried out in a selected diluentsuch that the polymer is only slightly soluble in the diluent, and thediluent is sufficiently soluble in the polymer so that a second phase isformed which contains substantially all of the polymer, but wherein thecontinuous phase or diluent phase has a sufficiently low viscosity sothat the second or polymer-rich phase can be dispersed therein. In oneform of these cement suspension polymerizations, they are carried out insuch a diluent whose lower critical solution temperature for the polymerto be prepared is below the temperature at which the reaction is to becarried out. The lower critical solution temperature, in turn, isdefined as the temperature above which the polymer is no longer solublein a solvent. In addition, in accordance with these processes, it wouldbe appreciated that as the temperature of a solution of polymer anddiluent is increased, a temperature will be reached above which thepolymer is no longer soluble. If maintained at this temperature,separation of two phases will occur with generally the lower portionbeing a heavier polymer-rich phase and the upper portion being a lightersolvent-rich phase. This phenomenon can thus be utilized to separatepolymers from solution in conventional solution polymerization processesas discussed above. In any event, to achieve the desirable two-phase"cement suspension" it is necessary that the light phase be a very poorsolvent for the polymer to maintain low viscosity, and that thepolymer-rich heavy phase separate out and contain enough solvent so itbehaves as a liquid and can be dispersed in the light phase. Theparticular details of such cement suspension processes are set forth inU.S. Pat. No. 3,932,371, and the description of same is herebyincorporated herein by reference thereto.

2. Halogenated Base Terpolymer Preparation

An example of a post-polymerization chemical modification reaction thatcan be run on bulk recovered polymer, and can also be run on polymersolution produced in a solution polymerization process (after suitablequenching and removal of residual monomers) is halogenation (e.g.,radical bromination) to produce the very versatile benzylichalogen-functional copolymer ingredients described herein. Thesurprising ease and highly selective nature of radical halogenation tointroduce a benzylic halogen, and the great versatility of the benzylichalogen, makes this a most preferred modification reaction.

Functionality-introducing reactions such as halogenation are carried outon the precursor para-methylstyrene/isobutene copolymers produced by anyof the above polymerization methods in a separate post-polymerizationstep, with direct halogenation, and most preferably radicalhalogenation, being the preferred reaction. It is generally desirable totreat the precursor polymerization copolymer product in an appropriatemanner, prior to such halogenation, in order to quench the catalystand/or remove catalyst residues, remove residual unconverted monomers,and put it into a convenient form for the halogenation reaction.

It is nearly always desirable to quench the catalyst in the reactoreffluent in order to prevent continued polymerization, with theconcomitant production of low molecular weight ends and/or to preventdegradation and crosslinking reactions from occurring as the effluent iswarmed. This quenching can be accomplished in a conventional manner.Generally speaking, with the aluminum-based catalysts usually employedin making the copolymers of this invention and with the high catalystefficiencies achieved, a separate catalyst residue removal step is notrequired, but much of this residue is extracted into the water phase inconjunction with conventional water-based finishing processes anyway.

Residual unconverted monomers left in the precursor copolymer will reactduring halogenation to both consume halogen and produce generallyundesirable by-products, and their presence thus renders it difficult tocontrol and measure the amount of desired functionality introduced intothe copolymer. Hence, except in cases where the copolymer has beenpolymerized at very high conversion, it is usually necessary to removethese residual monomers. Unreacted isobutene is volatile enough to beeasily removed in any of a variety of stripping operations, butpara-methylstyrene, with its high boiling point of 170° C., is much moredifficult to remove. It is therefore advantageous to polymerize at veryhigh para-methylstyrene conversion levels so that its removal and/orrecycle becomes unnecessary or, at least involves smaller amounts ofmaterial.

The halogenation reaction itself can be carried out in the bulk phase oron the precursor copolymer either in solution or in a finely dispersedslurry. Bulk halogenation can be effected in an extruder, or otherinternal mixer, suitably configured to provide adequate mixing and forhandling the halogen and corrosive by-products of the reaction. Bulkhalogenation in an extruder has the advantages of permitting completeremoval of residual unreacted para-methylstyrene by conventionalfinishing operations prior to halogenation, and of avoiding possiblediluent halogenation as an undesired side reaction. It has thedisadvantages of requiring a much more expensive and high poweredreactor (i.e., extruder) than is required for solution halogenation, andof providing poorer mixing, thermal control, etc., than can be achievedin solution, so that the halogenation reaction is conducted under lesshomogeneous, more difficult to control conditions. The details of suchbulk halogenation processes are set forth in U.S. Pat. No. 4,548,995,which is hereby incorporated herein by reference thereto.

Solution halogenation is advantageous in that it permits good mixing andcontrol of halogenation conditions to be achieved, easier removal ofundesired halogenation by-products, and a wider range of initiators ofhalogenation to be employed. Its disadvantages include the need forremoval of residual unreacted para-methylstyrone prior to halogenation,the presence of complicating side reactions involving solventhalogenation, and a solution step if a non-solution polymerizationprocess is used to prepare the copolymer, as well as removal, clean-upand recycle of the solvent. Suitable solvents for such halogenationinclude the low boiling hydrocarbons (C₄ to C₇) and halogenatedhydrocarbons. The halogenation can also be conducted with the copolymeras a fine slurry or cement suspension in a suitable diluent which is apoor solvent for the copolymer. This is advantageous from a viscosityviewpoint and allows high solids content during halogenation, but itrequires that the slurry or Suspension be stable with little tendency toagglomerate or plate out on reactor surfaces. Since the high-boilingpoint Para-methylstyrene makes its removal by conventional distillationimpractical, and since it is difficult to completely avoid solventhalogenation, it is very important where solution or slurry halogenationis to be used that the diluent and halogenation conditions be chosen toavoid diluent halogenation, and that residual para-methylstyrene hasbeen reduced to an acceptable level.

Halogenation of the precursor para-methylstyrene/isobutene copolymerintermediates is significantly different from halogenation ofisobuteneisoprene (butyl) rubbers because the primary reactive site forhalogenation is entirely different. The para-methylstyrene/isobutenecopolymers contain no in-chain (backbone) olefinic unsaturationcontribution from the para-methylstyrene, and the primary reactivehalogenation site is thus the enchained para-methylstyrene moiety, whichis far less reactive than the olefinic site in butyl rubber. Undertypical butyl rubber halogenation conditions (e.g., dark, non-catalyzedreactions, in a hydrocarbon solvent, at low temperature (such as lessthan about +80° C.) and for short contact times (such as less than about10 minutes)) no detectable halogenation of the para-methylstyrenecopolymer even occurs. Furthermore, while it is possible to chlorinatepara-methylstyrene copolymers in a polar diluent, the chlorinatedspecies produced are entirely different than in the case ofisobutylene-isoprene (butyl) rubber. Such chlorinated species includechlorine on the aromatic ring, and on the polymer backbone, as well asthe preferred primary benzylic chlorination, in contrast to thechlorination of the olefinic sites in the prior art copolymers.

With halogenation of para-methylstyrene/isobutene copolymers, it ispossible to halogenate the ring carbons, but the products are ratherinert and of little interest. It has surprisingly been found, however,that it is possible to introduce this desired functionality into thepara-methylstyrene/isobutene copolymers hereof in high yields and underpractical conditions without obtaining excessive polymer breakdown,crosslinking or other undesirable side reactions.

When halogenation of the para-methylstyrene/isobutene copolymers hereofis carried out without using the specified selected reaction conditions,catalysts, reagents and initiators hereof, it tends to either not occurat all, or to proceed by various routes, so as to produce a variety ofhalogenated products. Thus, if chlorine or bromine is added to asolution of para-methylstyrene/isobutene copolymer in a low dielectricconstant hydrocarbon solvent, such as hexane or cyclohexane, in the darkat 30°-60° C. for about five minutes, essentially no reaction occurs. Onthe other hand, if the chlorination reaction is run in a more polar(higher dielectric constant) diluent, such as methylene chloride, thenchlorination does occur, but apparently by many different routes, sothat a variety of different chlorinated products are produced thereby.These include some of the highly desirable primary benzylic chlorineresulting from substitution on the ring methyl group, but a major amountof less desirable chlorinated products.

It is known in connection with the halogenation of small molecules thatthe side chain halogenation of alkyl-substituted benzenes, as opposed tonuclear substitution, is favored by radical instead of ionic conditions.This might therefore be said to suggest that such radical conditions,including the avoidance of Friedel-Crafts catalysts (or metallichalogenation catalysts in general), the avoidance of polar diluents, andthe use of photochemical, thermal, or other radical initiators, would bepreferred for the selective halogenation of the copolymers hereof.However, it is also known that the halogenation of polymers does notnecessarily follow the same routes as that of these small molecules,particularly since even minor side reactions can be extremelysignificant. Furthermore, it is known that, in radical halogenation,with concurrent hydrogen replacement, tertiary hydrogens are more easilyreplaced than are secondary hydrogens, which are more easily replacedthan the primary benzylic hydrogens on the enchained para-methyl/styrylmoiety in the copolymers hereof.

It has rather surprisingly been found, however, that radical brominationof the enchained para-methyl styryl moiety in the copolymer ingredientsof this invention can be made highly specific with almost exclusivesubstitution occurring on the para-methyl group, to yield the desiredbenzylic bromine functionality. The high specificity of the brominationreaction can thus be maintained over a broad range of reactionconditions, provided, however, that factors which would promote theionic reaction route are avoided (i.e., polar diluents, Friedel-Craftscatalysts, etc.).

Thus, solutions of the precursor para-methylstyrene/isobutene copolymerintermediates of this invention in hydrocarbon solvents such as pentans,hexane or heptane can be selectively brominated using light, heat orselected radical initiators (according to conditions, i.e., a particularradical initiator must be selected which has an appropriate half-lifefor the particular temperature conditions being utilized, with generallylonger half-lives preferred at warmer halogenation temperatures) aspromoters of radical halogenation, to yield almost exclusively thedesired benzylic bromine functionality, via substitution on thepara-methyl group, and without appreciable chain scission and/orcross-linking. Without wishing to be bound by any theory, it is believedthat the bromination reaction proceeds by means of a rapid radical chainreaction with the chain carrier being, alternatively, a bromine atom anda benzylic radical resulting from hydrogen atom abstraction from apara-methyl group on the enchained para-methylstyryl moiety. Theproposed mechanism thus involves the following steps: ##STR9##

The reaction terminates when one of the radicals reacts with someradical trap in the system, or the radicals destroy themselves byrecombination or disproportionation.

This reaction can be initiated as shown in step (1) above by formationof bromine radicals, either photochemically or thermally (with orwithout the use of CH₃ sensitizers), or the radical initiator used canbe one which preferentially reacts with a bromine molecule rather thanone which reacts indiscriminately with bromine radicals, or with thesolvent or polymer (i.e., via hydrogen abstraction). The sensitizersreferred to are those photochemical sensitizers which will themselvesabsorb lower energy photons and dissociate, thus causing, in turn,dissociation of the bromine, including materials such as iodine. It isthus preferred to utilize an initiator which has a half life of fromabout 0.5 to about 2500 minutes under the desired reaction conditions,more preferably from about 10 to about 300 minutes. The amount ofinitiator employed will usually vary from about 0.02 to about 0.3percent by weight. The preferred initiators are bis azo compounds, suchas azobisisobutyronitrile, azobis(2,4-dimethylvaleryl)nitrile,azobis(2-methylbutyro)nitrile, and the like. Other radical initiatorscan also be used, but it is preferred to use a radical initiator whichis relatively poor at hydrogen abstraction, so that it reactspreferentially with the bromine molecules to form bromine radicalsrather than with the precursor copolymer or solvent to form alkylradicals. In those cases, there would then tend to be resultantcopolymer molecular weight loss, and promotion of undesirable sidereactions, such as crosslinking.

The radical bromination reaction of this invention is highly selective,and almost exclusively produces the desired benzylic brominefunctionality. Indeed, the only major side reaction which appears tooccur is disubstitution at the pard-methyl group, to yield the dibromoderivative, but even this does not occur until more than about 60percent of the enchained para-methylstyryl moieties have beenmonosubstituted. Hence, any desired amount of benzylic brominefunctionality in the monobromo form can be introduced into thecopolymers of this invention, up to about 60 mole percent of thepara-methylstyrene content. Furthermore, since the para-methylstyrenecontent can be varied over a wide range as described herein, it ispossible to therefore introduce a significant functionality range. Thehalogenated copolymer ingredients of this invention are thus highlyuseful in subsequent reactions, for example, crosslinking reactions.Once the bromide leaving group is incorporated, the copolymer can befunctionalized with a radiation-sensitive nucleophile compound.

It is desirable that the termination reactions discussed above beminimized during bromination, so that long, rapid radical chainreactions occur, and so that many benzylic bromines are introduced foreach initiation, with a minimum of the side reactions resulting fromtermination. Hence, system purity is important, and steady-state radicalconcentrations must be kept low enough to avoid extensive recombinationand possible cross-linking. The reaction must also be quenched once thebromine is consumed, so that continued radical production with resultantsecondary reactions (in the absence of bromine) do not then occur.Quenching may be accomplished by cooling, turning off the light source,adding dilute caustic, the addition of a radical trap, or combinationsthereof.

Since one mole of HBr is produced for each mole of bromine reacted withor substituted on the enchained para-methylstyryl moiety, it is alsodesirable to neutralize or otherwise remove this HBr during thereaction, or at least during polymer recovery in order to prevent itfrom becoming involved in or catalyzing undesirable side reactions. Suchneutralization and removal can be accomplished with a post-reactioncaustic wash, generally using a molar excess of caustic on the HBr.Alternatively, neutralization can be accomplished by having aparticulate base (which is relatively non-reactive with bromine) such ascalcium carbonate powder present in dispersed form during thebromination reaction to absorb the HBr as it is produced. Removal of theHBr can also be accomplished by stripping with an inert gas (e.g., N₂)preferably at elevated temperatures.

The brominated, quenched, and neutralized para-methylstyrene/isobutenecopolymers, "base terpolymer" of this invention can be recovered andfinished using conventional means with appropriate stabilizers beingadded to yield highly desirable and versatile leaving groupfunctionalized saturated copolymers which are useful in the nucleophilicsubstitution reactions which follow to incorporate UV- or otherradiation-reactive functionality.

In particular, since little if any tertiary benzylic bromine is producedin the copolymer molecule, the potential dehydrohalogenation reactionwill be almost entirely eliminated therein. This results in ahalogenareal polymer of improved stability. In addition, presence of thebromine on the ring-methyl group leads to several additional significantadvantages with respect to this product. It permits functionalization bysubstitution of other functional groups at that site.

3. Nucleophilic Substitution of the Base Terpolymer

The henzylic bromine (halogen) functionality is uniquely suited, as thebase from which the versatile functionalized saturated copolymersemployed in the lithographic or corrosion resistant coating compositionsof this invention can be prepared, because it can be made to undergoselective nucleophilic substitution reactions with a great range ofnucleophiles, so that almost any desired the and amount of functionalitycan be introduced without undesirable side reactions and underconditions which are mild enough to avoid degradation and/orcrosslinking of the saturated copolymer backbone containing the pendantbenzylic halbert functionality. Furthermore, in many instances, it ispossible to only partially convert the pendant benzylic halogen toanother desired functionality while retaining some, or to later convertanother portion, of the remaining benzylic halogen functionality to yetanother new functionality, so that copolymers containing mixedfunctionalities can be made. The mixed functionality can advantageouslyprovide unique combinations of properties, such as grafting with anotherfunctional poller via one of the functionalities and then cross-linkingor adhering to some surface via another of the functionalities.

One of the attributes of the benzylic halogen functionality of theradically halogenated isobutylene/para-methylstyrene copolymers whichmakes them an ideal base copolder from which to prepare the variousradiation-reactive functionalized saturated copolymers is the wide rangeto nucleophilic substitution reactions this benzylic halogenfunctionality will undergo and the relatively mild conditions underwhich these nucleophilic substitution reactions will proceed. A benzylichalbert functionality constitutes a very active electrophile which willreact under suitable conditions with any nucleophile capable of donatingelectrons to it. Suitable nucleophiles include those containing oxygen,sulfur, nitrogen, phosphors, carbon, silicon, and various metalsincluding especially magnesium, lithium, sodium, and potassium. SuitableUV-reactive nucleophiles include, for example, UV-reactive carboxylateesters, dithiocarbamate esters, and the like. Equally important to thisversatility in types of nucleophiles which will react with the benzylichalogen functionality is the relatively mild conditions under whichthese nucleophilic substitution reactions proceed so that substitutionreactions can be completed to introduce the desired new functionalitywithout cleavage or crosslinking reactions involving the saturatedhydrocarbon backbone of the isobutylene/para-methylstyrene copolymer.

Another of the attributes of the benzylic halogen functionality is theselectivity with which the desired substitution reactions can be made toproceed without undesirable side reactions. The benzylic halogenfunctionality will undergo clean substitution reactions withoutcomplicating elimination reactions. This attribute is extremelyimportant in reactions involving soluble high polymers, since even atiny amount of a side reaction which can lead to coupling may lead togelation. In reactions involving simple molecules (which are usuallymono-functional) yields of only 70 percent of the desired product may beacceptable, since purification and separation of the undesired productsis relatively simple. In reactions involving already cross-linkedpolymers (e.g. "Styragels") lower yields to the desired product may alsobe acceptable, since the starting polymer is already insoluble. However,in reactions with the soluble high polymers of this invention whichcontain many functional groups per molecule, it is necessary toachieve >99 percent of the desired substitution reaction in order tomaintain solubility during reaction and recovery. Tiny, almostinsignificant (in other reactions) amounts of side reactions whichproduce gel may interfere with usefulness. Furthermore, purification ofthe substituted polymer to remove unwanted side products is usually verydifficult or impossible. This is why the selective single route to highyield nucleophilic substitution reactions achievable with benzylichalogen functionality under controlled conditions is important. By usingisobutylene/para-methylstyrene/para-bromomethylstyrene terpolymers as a"base" polymer for modification, and by conducting nucleophilicsubstitution reactions under appropriate and controlled conditions,soluble, backbone-saturated copolymers containing useful pendantfunctionality have been prepared. Examples include:

(1) Esters (many containing other function groups such as acetate,stearate linoleate, eleostearate, cinnamate, etc.;

(2) Hydroxyl (attached directly in place of the benzylic bromine orattached via another linkage);

(3) Carboxy;

(4) Nitrile;

(5) Quaternary ammonium salts;

(6) Quaternary phosphonium salts;

(7) S-Isothiuronium salts;

(8) Dithiocarboxylate esters;

(9) Mercaptans;

(10) Carboxylate esters and phenolares which contain radiation-reactivefunctional groups exemplified by benzoylbenzoate, cinnamate, tung oilfatty acid esters, and anthraquinone-2-carboxylate; and

(11) UV-reactive dithiocarbamate esters.

While every reactive derivative, in general, and radiation-reactivederivative specifically, that could be prepared by nucleophilicsubstitution reactions on theisobutylene/para-methylstyrene/para-bromomethylstyrene terpolymers hasnot been prepared, it is obvious that one skilled in the art couldattach almost any desired pendant functionality including those havingradiation reactivity and mixtures of functionalities as desired forvarious applications, by applying the principles disclosed herein. Theattachment of two or more different types of functional groups allowspreparation of polymers which can be radiation crosslinked, emulsified,and/or possess improved adhesion to specific substrates as each of theseattributes can be derived from the judicious choice of an appropriatefunctionality.

The "key" requirements for producing the versatile, pendant radiationsensitive backbone saturated, soluble copolymers of this inventions viaselective nucleophilic substitution reactions are:

(1) Use of the isobutylene/para-halomethylstyrene/para-methylstyrenebase terpolymers for nucleophilic substitutions under appropriate,controlled conditions. The composition of the terpolymer can be variedas desired to yield the desired combination of properties (i.e. T_(g),hardness, flexibility, impact strength, functionality level, etc.).

(2) Choosing the nucleophile and reaction medium so as to achieve therequired intimate contact between the benzylic halogen attached to thebase terpolymer and the nucleophile. It should be recognized that insome instances this can be accomplished by using a different solvent orreaction medium for the polymer and for the nucleophile and thenemploying an appropriate phase transfer catalyst to promote thereaction.

(3) Achieving specific solvation at the reaction site so that thedesired nucleophilic substitution reaction is facilitated at mildconditions.

(4) Avoiding "vigorous" or "harsh" reactants or reaction conditions suchas strong "hard" bases or high temperatures that would cause a loss inreaction specificity and allow side reactions to become important and/orcause crosslinking or degradation reactions to occur.

(5) Choosing the nucleophilic reagent and promoters appropriately sothat the desired substitution reaction occurs quickly under mildconditions and potential undesired side reactions are avoided. Forexample, in using a carboxylic nucleophile in an esterification reactionto replace the benzylic bromines on anisobutylene/para-methylstyrene/para-bromomethylstyrene base terpolymer,one could choose the potassium salt of the acid as the nucleophilicreagent, along with 18 Crown-6 solvate the potassium ion and promote thedesired esterification substitution reaction, or one could choose thetetrabutylammonium counterion in an appropriate solvent as a nice "soft"acid to promote the reaction, rather than trying to use a "hard" ionicsalt of the carboxylic acid as the nucleophilic reagent.

(6) Choosing reaction conditions to minimize sequential reactions byrecognizing that the nucleophilic substitution reaction being conductedcan itself form attached pendant nucleophilic reagents on the basecopolymer backbone and that these already attached nucleophilic reagentscan nucleophilically "attack" other unreacted benzylic bromines on thebase terpolymer in a sequential manner to consume the desired, alreadyattached new functionality, and at the same time produce undesirablecrosslinking and gelation.

Thus, reaction conditions must be chosen such that the unreactednucleophilic reagent being used in the nucleophilic substitutionreaction is either a much stronger, more reactive nucleophile, or ispresent in great excess over any attached nucleophilic functionalityproduced in the substitution reaction. For example, it must berecognized that attached basic groups will become available nucleophilesunder basic conditions for further reaction with benzylic bromine. Theseintrapolymeric groups can react with other benzylic bromines to consumethe already attached pendant functionality and produce undesiredcrosslinks. The result is galled polymer instead of the desired pendantfunctionalized polymer of the invention. Attempting to replace thebenzylic bromines of the base terpolymer of this invention withmercaptan groups, it must be recognized that the attached SH (mercaptan)groups will form incorporated mercaptide nucleophilic reagents underbasic conditions and these incorporated mercaptide groups will reactwith other benzylic bromines to consume the already incorporated pendantmercaptan functionality and produce undesired thioether crosslinksresulting in gelled polymer instead of the desired pendantfunctionalized polymer of the invention.

Likewise, in producing a pendant hydroxy functionalized polymer of thisinvention, it must be recognized that the attached hydroxy groups willform alkoxide nucleophilic reagents under strongly basic conditions, andthese attached alkoxide groups can react in a sequential manner withother unreacted benzylic bromines of the base terpolymer to consume thealready attached pendant hydroxy functionality to produce ethercrosslinks, resulting in gelled polymer rather than the desired pendantfunctionalized polymer of this invention. The key requirement ofrecognizing the potential for sequential reactions and choosingconditions to minimize them is especially important in cases where it isdesired to produce the pendant radiation-reactive functionalizedsaturated polymers of this invention with mixed pendant functionality.In these mixed functionality polymers, it is extremely important tochoose functionalities and conditions such that the desired pendantfunctionalities are preserved and sequential reactions are avoided.

The polymers of isoolefin and para-alkylstyrenesilane derivatizedpolymers represent another broadly useful family of materials which canbe easily prepared by nucleophilic displacement .through the use ofsuitable nucleophilic silane reagents like (N,N-dimethyl-3-aminopropyl)silanes, as depicted below: ##STR10##

Wherein R¹, R² and R³ are each independently selected from the groupconsisting of hydrogen, chloro and alkoxy having from 1 to about 5carbon atoms such as methoxy, ethoxy, etc. The reactivity of thesederivatives can be varied based upon the number and type of silanespecies present.

The polymers of isoolefin and para-alkylstyrene containing Si--Cl bondsare the most reactive toward a variety of nucleophiles, including anucleophile as weak as water. Thus, these materials are vulcanizable byexposure to the atmosphere and are therefore very useful as roomtemperature vulcanizable compositions (RTVs).

Likewise, these polymers containing Si-O(alkyl) bonds are also reactivewith a variety of nucleophiles (though not as reactive as Si--Cl) whichalso include water. Again this reactivity can be exploited in RTVapplications, especially where the emission of neutral species duringcuring is preferred. Appropriate applications for this silane chemistryinclude sealants and adhesives where the silane functional group allowsfor crosslinking and improves adhesion to substrates such as glass.

Uniquely reactive are the polymers of isoolefin andpara-alkylstyrene-silane derivatives which contain Si--H bonds. Theyundergo three fundamental types of reactions. They can react withhydroxyl- or silanolfunctionalized materials in the presence of tinoctoate, zinc octoate and other metal salts to form bonds with theevolution of hydrogen. This reaction can be used to imparthydrophobicity to glass, leather, paper or fabric surfaces.

The Si--H functionality will react with olefins in the presence ofcertain free radical or precious metal catalysts. This reaction opensthe opportunity for addition cure (RTV) or low temperaturevulcanization. Mixtures of these polymers with another olefin containingpolymer like polybutadiene or vinyl functional silicones will rapidlyyield a intermolecular crosslinked system of the polymers of isoolefinand para-alkylstyrene and the other polymer. The polymers of isoolefinand para-alkylstyrene-vinyl silicone system will provide a usefulthermally stable crosslink system which exhibits improved permeabilityproperties over existing silicone systems.

The third useful reaction for these Si--H polymers of isoolefin andpara-alkylstyrene derivatives is as polymeric reducing agents. Si--Hcompounds are known to be active mild selective reducing agents fornitroaromatics, acid chlorides, aldehydes and ketones. Binding thesereagents to polymers offers the advantage of ease of separation; thepolymer is easy to remove from the low molecular weight reduced speciesand no hydrolysis of the remaining reagent is necessary prior toisolation. Another advantage is that these reductions can be run in thepresence of air and moisture in a wide range of solvent systemsincluding hexane, methylene chloride and dioxane.

The novel versatile, pendant functionalized, backbone saturated, solublecopolymers of this invention which are derived via selectivenucleophilic substitution reactions on a base terpolymer comprisingisobutylene/para-methylstyrene and para-bromomethylstyrene are widelyuseful as will be further disclosed in the examples dealing withspecific pendant functionalities. They encompass a broad range inproperties ranging from low T_(g) elastomers high in isobutylene to highT_(g) plastics high in para-methylstyrene with tough high impactcompositions at intermediate isobutylene contents. The presence ofappropriate pendant functionality renders this entire range of products"paintable" for use in external automotive or appliance applications,etc. and enables them to be adhered to and used as coatings on othersubstrates especially in exterior applications where the excellentenvironmental resistance of the backbone saturated copolymers isadvantageous. The presence of appropriate pendant functionality alsoenables these compositions to react with or be coreacted with otherfunctional polymers, or fillers, or fibers to form composite structures(i.e. laminates, dispersions, etc.) with desirable combinations ofproperties.

In accordance with this invention it has been found that the novel,pendant, radiation-reactive functionalized, saturated copolymersdescribed and exemplified herein can be conveniently and practicallyproduced by first preparing a base terpolymer comprising a saturatedhydrocarbon backbone with one or more pendant attached electrophilicmoieties, and then attaching the desired new radiation-reactivefunctionality via a selective nucleophilic substitution reaction withthe pendant attached electrophilic moieties. It has been found to bedesirable, and is important in obtaining the pendant functionalizedcopolymer ingredient of this invention, that the pendant attachedelectrophilic moieties which are replaced by other functionalities viaselective nucleophilic substitution reactions be benzylic halogenmoieties. These pendant attached electrophilic benzylic halogen moietiescan be readily inserted into random isobutylene/para-methylstyrenecopolymers by radical halogenation as mentioned previously to yield thebase terpolymer containing isobutylene/para-methylstyrene/and brominatedpara-methylstyrene securing random units. This base terpolymercontaining electrophilic benzylic halogen moieties is the "parent"polymer from which the novel, pendant functionalized, saturatedcopolymers of this invention are prepared via selective nucleophilicsubstitution reactions.

These novel pendant functionalized polymers of this invention arecomprised of the following "mer" units: ##STR11## wherein: R and R' areindependently selected from the group consisting of hydrogen, alkyl, andprimary or secondary alkyl halide, X is a halogen atom (preferablybromine or chlorine, and most preferably bromine), Y represents a newradiation-reactive group attached to the polymer via nucleophilicsubstitution of one of the benzylic halogens so that an enchained c"mer" unit has become a d "mer" unit, and Z represents a newnon-radiation-reactive group attached to the polymer via nucleophilicsubstitution of one of the benzylic halogens so that an enchained c"mer" unit has become an e "mer" unit. Actually, there can be severaldifferent Y and/or Z species in the same polymer in cases where mixedfunctionalities are being introduced. Y and Z are the residues whichbecome attached to the polymer enchained c "met" unit in place ofhalogen when a nucleophilic reagent capable of donating electrons tobenzyl halides is reacted with the base terpolymer in accordance withthis invention.

The four (or more if several different Y and/or Z functionalities arepresent) "mer" units are attached to one another in random fashion toform the novel, pendant radiation-reactive functionalized, backbonesaturated polymer ingredients in the compositions of this invention.Total polymer number average molecular weight can range from <500to >100,000. The amounts of the various "mer" can range as follows:

a) (isobutylene)--"mer" units from about 10 to about 99.5 weightpercent;

b) (p-alkylstyrene)--"mer" units from about 0.5 to about 90 weightpercent;

c) (radically brominated p-alkylstyrene)--"mer" units from 0 to about 55weight percent;

d) (pendant radiation reactive functional p-alkylstyrene)--"mer" unitsfrom about 0.5 to about 55 weight percent;

e) (pendant non-radiation-reactive functional p-alkylstyrene)--"mer"units from 0 to about 55 weight percent.

Actually, there can be several different Y and/or Z species in the samepolymer in cases where mixed functionalities are being introduced. Y andoptionally Z are the residues which become attached to the polymer unitin place of halogen when a nucleophilic reagent capable of donatingelectrons to benzyl halides is reacted with the base terpolymer inaccordance with this invention, wherein a) is from about 10 to about99.5 percent by weight, more preferably from about 80 to about 99percent by weight, and most preferably from about 90 to about 98 percentby weight, b). is from about 0.5 to about 90.0 percent by weight, morepreferably from about 1 to about 20 percent by weight, and mostpreferably from about 2 to about 10 percent by weight, d) is from about0.5 to about 55.0 weight percent by weight, more preferably from about0.5 to about 20 percent by weight and most preferably from about 0.5 toabout 15 mole percent, c) is from 0 to about 55.0 percent by weight ofthe para-alkylstyrne, more preferably from 0 to about 20 percent byweight, and most preferably from 0 to about 15 percent by weight and e)is from 0 to about 55.0 percent by weight, more preferably from 0 toabout 20 percent by weight, and most preferably from 0 to about 15percent by weight. The number average molecular weight of thefunctionalized polymers is from about 5000 to about 500,000, morepreferably from- about 50,000 to about 300,000 and most preferably fromabout 50,000 to about 150,000.

In accordance with an embodiment of the present invention, thenucleophilic reagents which are capable of donating electrons to benzylhalides and to displace a halide ion via a substitution nucleophilicdisplacement reaction and attach the radiation-reactive functional groupY, and optionally the non-radiation-reactive functional group Z, in thebenzylic position from which the halogen was displaced may be Y or YM,or Z or ZH, wherein: M is hydrogen, a metal ion, or an ammonium ion andY and/or Z are either a simple nucleophile containing oxygen, sulfur,silicon, carbon, nitrogen, phosphorus, or various metals; or Y and/or Zare a small molecule of <1000 molecular weight which may contain otherfunctionality in addition to the simple nucleophile which becomeattached at the benzylic position in the nucleophilic displacementreaction.

Examples of simple nucleophiles Containing oxygen which results in theattachment of --O-- to the benzylic position from which the halide ionwas displaced included, but are not limited to: ##STR12## Examples ofsimple nucleophiles containing sulfur which result in attachment of--S-- to the benzylic position from which the halide ion was displacedinclude (but are not limited to): ##STR13## Examples of simplenucleophiles containing silicon which result in the attachment of --Si--to the benzylic position from which the halide ion was displaced andn=1,2 or 3 include (but are not limited to): ##STR14##

Examples of simple nucleophiles containing carbon which result in theattachment of --C-- to the benzylic position from which the halide ionwas displaced included (but are not limited to): ##STR15## Examples ofsimple nucleophiles containing nitrogen which result in the attachmentof --N-- to the benzylic position from which the halide ion wasdisplaced and n=0,1,2 or 3 (include but are not limited to): ##STR16##Examples of simple nucleophiles containing phosphorous which result inattachment of --P-- to the benzylic position from which the halide ionwas displaced and n=0,1,2 or 3 (include but are not limited to):

    PH.sub.n R.sub.3-n as in various phosphines

Examples of simple nucleophiles containing a metal which results in theattachment of --M-- to the benzylic position from which the halide ionwas displaced include (but are not limited to):

    Mg--(anthracene complex in THF)

    Li--(appropriately complexed)

Examples in which Y and/or Z are a small molecule of <1000 molecularweight containing other functionality in addition to the simplenucleophile which becomes attached at the benzylic position from whichthe halide ion was displaced in the nucleophilic displaced reactioninclude (but are not limited to): triethanol amine, iminodiacetic acid,iminodiacetonitrile, iminodiethanol, vinyl pyridines, cinnamate,eleostearate, linoleate, acrylate, benzoyl benzoate, benzoyl phenolate,dihydroxybenzophenone, crown ethers derivatives, cryptand derivatives,cellulose derivatives, sugar derivatives, low molecular weightpolyethylene oxide or polypropylene oxide chains with terminalnucleophilic groups, etc. It should be noted that these reactions inwhich Y and/or Z contain other functionalities in addition to the simplenucleophile which becomes attached at the benzylic position from whichthe halide ion was displaced greatly extend the type and range offunctionalities which can be incorporated into the novel pendantfunctionalized, saturated copolymers of this invention, as prepared byselective nucleophilic substitution reactions. This ability to attachmultifunctional Y and/or Z groups enables clusters of polar groups to beattached as is desirable in dispersants of various type (i.e. lube oildispersants); enables functionalities that are not readily achieved bythe nucleophilic displacement reaction (such as olefins or conjugatedunsaturation) to be attached; and enables very complex and specialfunctionalities such as chiral compounds or crown compounds of cryptandsto be attached to produce novel pendant functionalized copolymers ofthis invention with unique properties for highly specializedapplications such as catalysts and so forth.

However, it should also be noted that attachment of Y and/or Z groupscontaining other functionalities requires even greater care during thenucleophilic displacement reaction by means of which the Y and/or Zgroups are attached to insure that the new functionalities are preservedand are not consumed by sequential reactions to produce unintendedcrosslinking or gelation. In some instances, it may be desirable toblock the functionalities that need to be preserved until thenucleophilic substitution reaction is completed.

Most nucleophilic substitution reactions of this type also involve somedegree of side reactions which can be extremely detrimental in makingthe pendant functionalized soluble copolymers of this invention, sinceeven minor amounts of side reactions in high polymers can lead tounintended gelation which can greatly diminish utility. One advantage ofusing the unique base polymers of this invention for the nucleophilicsubstitutions reactions is that the undesired side reactions can belargely eliminated. It is known that nucleophilic substitution reactionscan proceed by several different mechanisms, and with most electrophilesthese different mechanisms can lead to different products or todifferent amounts of side reactions.

Those reactions which proceed by a concerted S_(X) 2 mechanism usuallyyield more of the desired substitution product than those proceeding byan S_(X) 1 mechanism. An advantage of using the enchained benzylichalogen of this invention as the electrophile site for nucleophilicsubstitution is that elimination reactions are entirely prevented sothat even nucleophilic substitution reactions proceeding by an S_(X) 1mechanism still lead selectively to the desired substitution productwithout undesired side reactions.

A further advantage of using the preferred benzylic bromine of thisinvention as the site for nucleophilic substitution is that thesubstitution reactions proceed under mild conditions (since the benzylicbromine is so labils) so that degradation of the polymer backbone orthermal rearrangement or decomposition of the reactants or products canbe avoided. Utilization of benzylic halogen, especially benzylicbromine, as the enchained electrophile site for nucleophilicsubstitution as in this invention also makes it possible to selectreagents and conditions so that other side reactions, such as thoseproceeding by another mechanism or the sequential reactions can belargely eliminated so that the soluble pendant functionalized copolymersof this invention can be prepared by selective S_(X) 2 nucleophilicsubstitution reactions.

Careful observance of the six "key" requirements already outlined isnecessary in order to prepare the radiation-reactive pendantfunctionalized backbone saturated, soluble polymers of this invention.

The exact and specific conditions suitable for preparing the variouspendant radiation-reactive functionalized, soluble, saturated copolymersof this invention will vary depending upon the new functionality beingintroduced, as well as the base copolymer composition and other factors,and some experimentation may be necessary to define practical conditionsin each case, but the same key factors as outlined herein must always beconsidered and observed. This will become clearer in the specificexamples to follow, but some general reaction conditions can first bedefined.

The nucleophilic substitution reactions can be run in solution using asolvent system in which both the base polymer and nucleophilic reagentare soluble; can be run in a two-phase liquid run system with the basepolymer dissolved in one phase and the nucleophilic reagent in theother; can be run in a two-phase solid/liquid system (i.e. with the basepolymer dispersed in a liquid phase containing the nucleophilicreagent); or can be run in bulk with reactants dissolved or dispersed inthe base polymer. The common solution situation is most controllable andgenerally the preferred case, but the bulk reaction may be economicallyadvantageous in some cases where suitable reagents and reactionconditions can be found.

The intermediate two-phase system may be advantageous under somecircumstances and may be necessary in instances where the solubilityparameters of the base polymer (containing the electrophile) and thenucleophilic reagent are so different that no common solvents exist. Inthese two-phase cases, it is often or usually desirable to use phasetransfer catalysts to promote the nucleophilic substitution reaction atthe interface between the phases or to transport the nucleophilicreagent to the electrophile site in the base polymer. A most preferredway of preparing the pendant functionalized polymers of this inventionis to radically halogenate a random isobutylene/para-methylstyrenecopolymer, as taught previously, to introduce the benzylic halogenelectrophile, and then conduct the nucleophilic substitution reaction tointroduce the desired new functionality in the same medium in asequential reaction (halogenate and then nucleophilically displace thehalogen) without ever recovering the base halogenated polymerseparately.

Depending upon the reactivity of the nucleophilic reagent used and thereaction conditions, the nucleophilic substitution reactions can be runat temperatures varying from about 0° C. to about 200° C. as limited bythermal stability of the nucleophilic reagent, the base polymer and thefunctionalized product polymer. Normally, temperatures between about 0°C. and about 150° C. are preferred. Reaction times are normally (but notnecessarily) chosen to allow the nucleophilic displacement reaction togo to completion (i.e. exhaustion of either the electrophile or thenucleophilic reagent) and may range between several seconds and a fewdays. Normally, reaction times between a few minutes and several hoursare preferred and reaction temperature and other conditions are set tomake a convenient reaction time possible.

A wide range of solvents and/or solvent blends may be used as the mediumin which the nucleophilic displacement reaction is run and it is thisfactor which determines whether a solution, dispersion, or bulk reactionis conducted. A number of factors are important in selection of the thesolvents. They need to be inert under the reaction conditions, easilyremoved from the product, easily recycled for reuse in the process, oflow toxicity under use conditions with minimum environmental healthconcerns, and economical to use. In addition, the solvents need toprovide a reaction environment which is favorable for the reaction beingrun, that is, they must bring the reactants into the required intimatesolution contact and should provide solvation stabilization forintermediate states along the desired reaction route. It is frequentlynecessary or desirable to use a blend of solvents to best achieve thevarious compromises required, with one solvent being an easily-handledgood solvent for the base polymer and the other being a good solvent forthe nucleophilic reagent and/or providing solvation stabilization forthe reaction intermediates. It is most preferred that the chosen solventsystem be one that is suitable for both the radical halogenationreaction to introduce the benzylic halogen electrophile into the randomisobutylene/para-methylstyrene copolymer, as well as for thenucleophilic substitution reaction to introduce the new pendantfunctionality, so that a sequential reaction route is feasible withouthaving to recover the halogenareal base polymer separately.

Solvents which are particularly suited for this sequential reactionroute vary somewhat depending upon composition of the base polymer, butwith the elastomeric base polymers high in isobutylene are the lowboiling saturated hydrocarbons (C₄ -C₇) or halogenareal hydrocarbons (C₁-C₇). Often it is desirable to add a more polar cosolvent, such as a lowboiling alcohol (C₁ -C₄) during the (second) nucleophilic displacementreaction in order to dissolve and carry-in the nucleophilic reagent, aswell as provide solvation stabilization for the nucleophilicdisplacement reaction. Aromatic solvents such as benzene, toluene, andchlorobenzene are generally good solvents for the base polymer over theentire composition range and provide a reaction medium favorable formany nucleophilic displacement reactions, but often present otherproblems (i.e. the toxicity of benzene or the high reactivity of tolueneduring radical halogenation which makes it unsuitable as the reactionmedium during this first stage of the sequential reaction route).Preferred solvent composition changes as composition of the base polymeris changed and depends upon whether it is desired to run the reactionsin solution or dispersion. In general, solvents of higher solubilityparameter containing some aromaticity or halogen are required forsolution reactions with the tougher, higher T_(g) base polymers of thisinvention which contain higher para-methylstyrene contents.

Similar considerations apply when considering the nucleophilicdisplacement reaction separately in order to run this reaction insolution, a good solvent for the base polymer (depending upon itscomposition) is required and a cosolvent for the nucleophilic reagentmay also be desirable or required. Good solvents for the base polymerare similar to those cited above as being suitable for the sequentialreaction route, but a broader range o f solvents can be considered sinceinertness during radical halogenation is not required. The low boilingsaturated hydrocarbons (C₄ -C₇) or halogenated hydrocarbons (C₁ -C₇) andaromatic hydrocarbons or naphthenes are preferred. Where greater solventpolarity is desired, tetrahydrofuran can be employed or good solvatingagents such as dimethyl formamide or dimethyl sulfide can be added. Thelatter solvents are also good solvents for many of the nucleophilicreagents and may be employed along with alcohols or ketones to dissolvethe nucleophilic reagent for addition to the base polymer solution. Thistechnique of adding a solution of the nucleophilic reagent (in a solventmiscible with that used for the base polymer) with rapid stirring to thebase polymer solution often results in a fine dispersion of thenucleophilic reagent so that even in cases where the nucleophilicreagent is not completely soluble in the mixed solvent resulting afterthe addition, an essential solution nucleophilic displacement reactioncan still be run because the nucleophilic reagent dissolves duringreaction to replenish the solution concentration as the reactionprogresses.

In more extreme cases, where the nucleophilic reagent is not soluble inco-solvents miscible with the base polymer solvent, or where thesolubility of the nucleophilic reagent in mixed-solvency (which willretain the base polymer in solution) is too low, then a two-phasereaction may be run with the base polymer dissolved in one phase and thenucleophilic reagent in the other. In such cases, good mixing isessential to provide lots of interfacial contact between the reactants,and a phase transfer catalyst is generally desirable to aid intransporting the nucleophilic reagent to the benzylic halogenelectrophile site on the base polymer. An example might be highly polarwater soluble nucleophilic reagents such as potassium cyanide, sodiumsulfite, or nitrilotriacetic acid. Examples of phase transfer catalystsuseful in these two phase reactors include (but are not limited to):tetrabutylammonium bromide, tetrabutylaramoniumbisulfate,tetrabutylaramonium hydroxide, benzyl triethylammonium chloride,tetrabutylphosphonium bromide, crown ethers, cyptands, Adogen 464, etc.These same types of materials are sometimes beneficial in speeding upthe one-phase solution reaction by providing specific solvation at thereaction site.

The most convenient reaction condition is to run a bulk reaction withthe nucleophilic reagent dissolved or dispersed in the base polymer.Working with high solids eliminates the costs of solvent handling andrecycle. However, the bulk reaction requires use of an expensiveinefficient reactor such as an extruder which is capable of providingmixing in highly viscous systems and restricts the reaction medium sothat only selected nucleophilic displacement reactions are possible, andeven those are more prone to involve side reactions because of the morerestrictive conditions and poorer mixing which prevails during reaction.

In addition to the general reaction considerations already discussed,the factors known to influence nucleophilic substitution reactions (bythose skilled in the art) may be applied in making the pendantfunctionalized polymers of this invention without materially affectingthe invention. Thus, reaction routes and activation energy can becontrolled by specific solvation, or catalysts, undesired reactions canbe prevented by blocking, etc.

EXAMPLES

These examples describe the specific preparations of several derivativesof the benzylic bromide copolymer and their uses in lithographic,corrosion resistant and other coating applications.

Gel refers to the insoluble residue of rubber in the adhesive and isdetermined by exhaustive solvent extraction of soluble polymer inrefluxing toluene for about 72 hours, then drying and weighing theremaining residue.

The coatings were prepared by dissolving the polymers or formulations intoluene and knife coating onto MYLAR or release paper. The coatingthicknesses were then dried and irradiated. The coatings thicknesseswere typically 1.5 mil. UV irradiation was conducted on an AmericanUltraviolet Mini-Conveyorized Curing System. UV dosages were determinedusing the UVA cure radiometer manufactured by EIT. EB crosslinking wasperformed on an Energy Sciences CB-150 Electrocurtain Electron BeamAccelerator.

Example 1 Preparation of Brominated Base polymer

A sample isobutylene/para-methylstyrene/para-bromomethylstyrene baseterpolymer was prepared as follows:

A 500 ml reaction flask fitted with a thermometer, stirrer, and droppingfunnel was set up in a glove box having an oxygen- and moisture-freenitrogen atmosphere, and the flask was cooled to -98° C. by immersion ina controlled temperature liquid nitrogen cooled heat transfer bath. Thereactor was charged with 386.6 g purified dry methyl chloride (having apurity of 99.8%), 47.4 g purified, dried and distilled polymerizationgrade isobutylene (having a purity of 99.9%), and 2.6 g purified, driedand vacuum-distilled para-methylstyrene (2.5 mole % of total monomers).Seventeen ml of a catalyst solution consisting of 0.19 weight percentethyl aluminum dichloride (EADC) in methyl chloride was allowed to dripslowly into the feed blend from the dropping funnel over the course of12 minutes while stirring and attempting to maintain temperature byimmersion of the reactor in the heat transfer bath. Despite the effortsat cooling, reactor temperature rose from -98° C. to -80° C. due to theexothermic polymerization reaction, and a slurry of polymer in aslightly tannish-colored liquid was formed. Some of the polymeragglomerated on the stirrer and reactor walls. The reactor was quenchedby adding 25 ml of cold methanol to yield an agglomerated mass of whitepolymer in a clear colorless liquid. The polymer was recovered byallowing the methyl chloride to flash off and kneading and washing thepolymer in methanol: 0.2 weight percent butylated hydroxytoluene (BHT)was added as an antioxidant and the polymer was dried in a vacuum ovenat 80° C. Fifty grams of dried white, opaque, tough, rubbery polymerwere recovered. conversion was 100% with a quantitative recovery of thepolymer. Catalyst efficiency was about 1550 grams of polymer/gram ofEADC. The recovered polymer had a viscosity average molecular weight(M_(v)) of 458,000, and contained 5.2 weight percent (2.5 mole percent)para-methylstyrone. Gel permeation chromatography (GPC) analysis usingultraviolet (UV) and refractive index (RI) detectors showed thepara-methylstyrene to be uniformly distributed over the entire molecularweight range indicating that a compositionally homogeneous copolymer hadbeen formed.

The GPC was performed using a Waters 150-C ALC/GPC (MilliporeCorporation) with a Waters Lambda-Max Model 481 LC UV Spectrophotometeron line. Data were collected and analyzed using customized softwaredeveloped with Computer Inquiry Systems, a division of Beckman Inc.Tetrahydrofuran was used as the mobile phase at various flow rates, butgenerally 1.0 ml/min. The instruments operated at 30° C. at a wavelengthof about 254 nm for the UV. The polyisobutene backbone has negligibleabsorbance compared to the aromatic ring at this wavelength. Columnsused were α Styragel (Waters) or Shadex (Showa Denko). Sets of columnsof wide porosity range were calibrated with narrow molecular weightdistribution polystyrene standards with molecular weights from 10³ to4×10⁶. Molecular weights are reported in terms of the polyisobutylenebackbone using a universal calibration. The output from the UV anddifferential refractometer detectors can be compared quantitatively tocalculate deviations in composition from the mean. Generally, viscosityaverage molecular weights are based on separate measurements indiisobutene at 20° C.

The high molecular weight random uniform copolymer of para-methylstyreneand isobutene prepared as above was dissolved in dried normal hexane ina two-liter baffled and jacketed resin flask set up for bromination witha four-neck resin flask top. An air-driven turbine mixer was used toprovide efficient mixing, and a thermometer and thermocouple were usedto measure and control the temperature, which was adjusted as notedhereinbelow by circulating a controlled temperature heat transfer fluidthrough the Jacket. One of the necks was used for mounting a droppingfunnel containing the bromine solution, which was added dropwise intothe reactor. The funnel and reactor were foil-wrapped to exclude light.A nitrogen bubbler tube with a sintered glass frit at the end wasmounted in one of the necks, with the frit immersed in the reactorsolution to provide nitrogen sparging at a rate which was set andcontrolled by a rotometer. The fourth neck was connected by plastictubing to a knock-out trap and caustic scrubber in order to .maintainseveral inches of water positive pressure during reaction, and to absorband neutralize any HBr and bromine vapors given off during the reaction.

The bromine solution was prepared by adding a weighed amount of bromineto pure mole-sieve dried n-hexane (essentially olefin-free) in thedropping funnel, and mixing to form less than a 30% solution. Thefoil-wrapped (to protect from the light) bromine dropping funnel wasthen mounted on the stirred, temperature-controlled, nitrogen-purgedreactor, and a 500 watt tungsten light bulb was mounted immediately nextto the reactor. The reactor was heated to 40° C. and the brominesolution added dropwise. The bromine charge was 5 percent by weight ofthe copolymer, and the reaction occurred rapidly as the bromine wasadded, as evidenced by rapid HBr evolution and rapid fading of the colorof the solution. Bromine was added over the course of two minutes, andthe reaction was quenched with excess caustic ten minutes after bromineaddition had been initiated. The quenched solution then was washed withwater, and the brominated copolymer was recovered by alcoholprecipitation and vacuum oven drying as previously described. BHT andtetramethylthiuram disulfide were mixed into the copolymer at 0.1% byweight as stabilizers prior to drying. The recovered brominatedcopolymer was soluble in diisobutylene, had an M_(v) of 254,000, andincluded 1.26 wt. % bromine as measured by Dietert analysis. Analysisusing 400 MHz NMR showed the presence of 0.9 mole % benzylic bromidegroup, with no other brominated structures detectable. GPC analysisusing UV and RI detectors showed the brominated copolymer to be auniform, homogeneous compositional distribution, narrow molecular weightdistribution (M_(w) /M_(n) -2) functional copolymer.

Example 2 Preparation of Pendant FunctionalizedIsobutylene/Para-methylstyrene Copolymer Containing Quaternary AmmoniumSalt Groups Example 2A

In this example, a tough ionically crosslinked quaternary ammonium saltderivative of a randomisobutylene/para-methylstyrene/para-bromomethylstyrene base terpolymerwas prepared. The base terpolymer was prepared in accordance with theprocedure of Example 1. A random isobutylene/para-methylstyrenecopolymer containing 2.4 mole percent para-methylstyrene and having aMooney viscosity of 30 (M_(L) (H8) @125° C.) was polymerized in acommercial 1800 gallon butyl polymerization reactor and then radicallybrominated using VAZO 52 initiation in hexane solution in a 100 gallonglass-lined Pfaudler Br reactor to give a base terpolymer with a Mooneyviscosity of 29 containing 2.6 weight percent bromine. The baseterpolymer composition was 1.4 mole percent para-bromomethylstyrene(including 0.1 mole percent dibrominated para-methylstyrene) 0.9 molepercent unbrominated para-methylstyrene and 97.7 mole percentisobutylene (there was a small amount of dibromination and slightmolecular weight loss due to the relatively high bromination level of 61percent of para-methylstyrene "mer" units. In the nucleophilicsubstitution reaction, 450 g of the base terpolymer were dissolved in2800 g of toluene in a 5 l resin flask under slight nitrogen purge andconnected through a reflux condenser to a scrubber and bubbler toproduce a 13.85 weight percent polymer solution. Then 47.2 g of triethylamine dissolved in 700 g of isopropanol were added slowly with stirringto give an 11.4 weight percent solution of base terpolymer in an 80/20toluene/isopropanol solvent blend with a molar ratio of 3 molestriethanol amine per mole of benzylic bromine. The solution was thenheated with stirring to the reflux temperature of about 85°-86° C. underslight nitrogen purge. The solution was stirred and refluxed for 6 hoursand then allowed to cool under nitrogen. A trial on a sample aliquotshowed that the solution emulsified when shaken with water orwater/alcohol (70/30) mixtures so it could not be washed. The emulsionshad a pH of S. The emulsions remained stable when acidified and evenwhen the pH was raised to 10-11 with NaOH solution, the solution wouldstill not separate well. Therefore, the functionalized polymer wasrecovered by precipitation and kneading in isopropanol and furtherseparated from unreacted triethyl amine by redissolving in atoluene/isopropanol blend and Precipitation in isopropanol. The purifiedfunctionalized polymer was vacuum oven dried at 70° C. after 0.2 weightpercent BHT had been mixed in as an antioxidant. The dried recoveredpolymer was a spongy, slightly off-white, extremely tough, ionicallycrosslinked elastomer. The pendant cationic quaternary ammonium saltgroups which had become attached to the "base" terpolymer bynucleophilic displacement of the benzylic bromines self-associated togive a tough ionically crosslinked elastomer. It was insoluble inhydrocarbons or alcohols but readily dissolved in a 90/10toluene/isopropanol mixed solvent which disrupted the ionic crosslinksby solvation. The nucleophilic displacement reaction is shown below:##STR17## Analysis as summarized below showed that essentially completesubstitution of benzylic bromines had occurred to give the pendantquaternary ammonium salt functionalized polymer.

    ______________________________________                                                   ANALYSIS                                                                      STARTING  PENDANT                                                             BASE      FUNCTIONALIZED                                                      TERPOLYMER                                                                              COPOLYMER                                                ______________________________________                                        M.sub.v      270,000     270,000                                              Weight percent Br                                                                          2.6         2.2                                                  Weight percent H                                                                           --          0.34                                                 NMR                                                                           Mole percent 1.4         --                                                   Benzylic Br                                                                   Mole percent --          1.4                                                  quat.                                                                         Mole percent 0.9         0.9                                                  para-methylstyrene                                                            ______________________________________                                    

The proton NMR spectrograph showed the disappearance of the resonancesat 4.47 ppm due to the benzylic hydrogens adjacent to the bromine andthe appearance of two new resonances: one at 4.7 ppm due to the benzylichydrogens adjacent to the quaternary nitrogen and another at 3.5 ppm dueto the methylene hydrogens adjacent to the quaternary nitrogen. Theresonances at 2.3 ppm due to the paramethyl hydrogens of the enchainedpara-methylstyrene "mer" units remained unchanged by the nucleophilicsubstitution reaction:

Proton NMR Resonances For Enchained "Mer" Units

    ______________________________________                                        PROTON                RESONANCE (ppm)                                         ______________________________________                                         ##STR18##            2.3                                                      ##STR19##            4.47                                                     ##STR20##            3.5                                                      ##STR21##            4.7                                                     ______________________________________                                    

A portion of the dried pendant functionalized polymer of this examplewas dissolved in a 90/10 hexane/isopropanol solvent blend to give a 15weight percent solution. This solution was cast on a glass plate and thesolvent was allowed to evaporate to deposit a tough rubbery film. Dryingwas completed in a vacuum oven at 70° C. An extremely tough ionicallycrosslinked film with excellent adhesion to the glass was deposited inthis way. The film could be dissolved off again with the mixedhydrocarbon/alcohol solvent blend. In a similar manner, a film of toughionically crosslinked elastomer was deposited on several poroussubstrates (i.e. coarse woven fabrics) by impregnating the substrateswith the solution by dipping and then allowing the solvent blend toevaporate to produce a proofed fabric coated with a tough ionicallycrosslinked elastomer. The proofed fabrics were water resistant withwater droplets simply beading-up and running off when applied. Theelastomers would also be expected to possess the high germicidalproperties characteristic of quaternary ammonium salts. This quaternaryammonium salt functionalized polymer would also be useful in many waterbased adhesives and binder applications where its high strength,toughness, water resistance, germicidal properties, environmentalresistance and good aging properties would be beneficial. It would alsofunction well as a corrosion-resistant coating on metals where the waterresistance, environmental resistance, good adhesion andcorrosion-inhibiting properties of cationic ionomers would be desirable.The ability to self-crosslink through ionic associations without theneed to add vulcanization agents (with their attendant problems ofextractability, toxicity, cost, etc.) or be subjected to a heatedvulcanization step is a highly desirable property of this cationicallyfunctionalized polymer.

Example 2B

In this example a pendant functionalized primarily isobutylene-basedcopolymer containing a cationic quaternary ammonium salt group wasprepared and converted to an emulsion-free stable latex. Anisobutylene-based polymer with an M_(v) of 45,000 and containing 2 molepercent para-chloromethylstyrene "mer" units was dissolved in a 70/30toluene/isopropanol solvent blend to form a 35 weight percent solutionby overnight shaking in a 2 gallon container. This solution was chargedalong with 1.4 times the stiochiometric amount of triethyl amine (basedon the amount of benzylic chlorine) to a 5 l "ell" resin flask set-up asdescribed in Example 2A and heated to 82° C. with stirring for 4 hoursto complete the nucleophilic substitution reaction. Recovery of a sampleof the pendant functionalized copolymer for analysis is outlined inExample 2A. Recovery steps include precipitation and kneading inisopropanol, resolution in toluene/isopropanol and reprecipitation inisopropanol before vacuum-oven drying at 70° C. with 0.2 weight percentBHT mixed in as an antioxidant. The purified and dried pendantfunctionalized copolymer was an extremely tough white crumb ionicallycrosslinked as shown by its insolubility in toluene but ready solubilityin a 90/10 toluene/isopropanol solvent blend. Analysis showed thatcomplete conversion of benzylic chlorines to quaternary ammonium saltgroups had occurred. The recovered copolymer contained 0.48 weightpercent nitrogen and NMR analysis showed the presence of 2 mole percentbenzyl triethyl ammonium chloride salt groups.

The balance of the cooled reaction effluent solution was simply mixed asis with distilled water at a 40/60 water/solution ratio by volume togive a stable oil-in-water emulsion which was refined first with adispersator and then in a colloid mill to give a very stable fineparticle size raw latex. The raw latex was stripped by heating withstirring under nitrogen to remove the solvents and part of the water togive a stable finished latex containing 50 percent solids. Noemulsifiers were required in making the latex and the preparation andstripping were accomplished easily without the foaming problems normallyexperienced in repairing, stripping and concentrating latices containingadded soaps as emulsifiers.

Castings from the finished latex dried to clear, hydrophobic, rubbery,tough, ionically crosslinked films as described for the solution castfilms of Example 2A. This emulsifier-free cationic latex makes possiblethe use of this tough, ionically crosslinked cationically functionalizedpolymer in a host of applications, including dipped goods, binders,nonwovens, coatings, radiation crosslinkable pressure sensitiveadhesives, etc., which could benefit from its excellent aging andenvironmental resistance along with its other unique properties.

Example 3 Preparation of Pendant Functionalized Isobutylene/SubstitutedPara-methylstyrene Copolymer

Containing Quaternary Phosphonium Salt Groups

In this example, a pendant functionalized primarily isobutylene-basedcopolymer containing cationic quaternary phosphonium salt groups wasprepared and converted to a stable, emulsifier-free latex. Anisobutylene-based polymer with an M_(v) of 17,000 and containing 1.9mole percent para-chloromethylstyrene "mer" units was dissolved in adried 75/25 heptane/isopropyl alcohol solvent blend under nitrogen toform a 40 weight percent polymer solution in a 5 l well resin flask. Thereactor was connected through a dry ice-cooled cold finger (setup toreflux condensables back into the flask) to a scrubber for vented gasesand bubbler to maintain several inches of water positive pressure on thereactor. A slow dry nitrogen flow was maintained through the system tomaintain the reactants under a dry, inert atmosphere. With stirring at25° C. and while maintaining the dry nitrogen seal, twice thestoichiometric amount of triethyl phosphine (on benzylic chlorine) as a67 weight percent solution in isopropanol was added dropwise from asealed dropping funnel. The mixture was heated with stirring to thereflux temperature of 77° C. and refluxed for 2 hours under nitrogen andconstent stirring before being cooled. A sample of the pendantfunctionalized polymer was recovered from the resulting clear effluentsolution for analysis. The recovery process comprised the steps ofprecipitation and kneading in isopropanol, resolution inhexane/isopropanol solution, and reprecipitation from isopropanolfollowed by vacuum-oven drying at 70° C. with 0.2 percent BHT mixed inas an antioxidant. Despite the very low molecular weight, the recoveredpolymer was a tough elastomeric ionically crosslinked polymer veryunlike the soft, sticky, semi-fluid starting base terpolymer. Analysisshowed it contained 0.95 mole percent phosphorus indicating about 50percent conversion of benzylic chlorines to quaternary phosphonium saltgroups had occurred.

The remaining cooled solution from the nucleophilic substitutionreaction was simply mixed as is with distilled water a 40/60water/solution ratio by volume to give a stable oil-in-water emulsionwhich was refined and then stripped and concentrated as in Example 2B togive a stable, emulsifier-free, fine particle size, cationic, latex at50% solids by weight. As in Example 2B, the latex preparation andstripping was accomplished easily without foaming problems, and castingsfrom the latex dried to hydrophobic, clear, tough, ionicallycrosslinked, elastomeric films which would be useful in a broad spectrumof applications as already outlined. The pendant functionalized polymerof this latex contained mixed functionalities, including benzylicchlorines and quaternary phosphonium chloride salt groups because thenucleophilic substitution reaction had not gone to completion.Nevertheless, the presence of 1 percent by mole quaternary phosphoniumchloride salt groups was adequate to permit preparation of the stableemulsifier-free latex, and was adequate to provide ionic crosslinking indeposited polymer films. The presence of the benzylic chlorine wouldpermit permanent covalent crosslink to be formed in many ways or permitother reactions to be run on this useful pendant functionalized polymer.

The nucleophilic substitution reaction is shown below: ##STR22##

Analysis showed that the reaction was accomplished without degradationor crosslinking and under the conditions of this experiment achieved a50 percent conversion of benzylic chlorines to quaternary phosphoniumchloride salt groups. Higher conversions could be achieved with longerreaction times and/or higher reaction temperature or by choosing a morefavorable reaction medium.

Examples 2 and 3 all show that the backbone saturated pendantfunctionalized copolymers of this invention containing various cationicpendant functionality are readily prepared by following the proceduresof this invention and that they have useful combinations of propertiesfor various applications. The pendant cationic groups are capable ofimparting self-emulsification properties to make possible the facilepreparation of emulsifier-free cationic latices and the pendant cationicgroups self-associate in dry deposited films to provide ionic crosslinkswhich are reversible by proper solvation.

Two classes of cationic pendant functionalized copolymers have beenexemplified (i.e. quaternary ammonium salts and quaternary phosphoniumsalts), but others such as the sulfonium salts, for example, usingthioethers as the nucleophile as shown below are also possible:##STR23##

Properties of these cationic pendant functionalized polymers can bevaried and controlled by the type of cationic group attached as well asby the R groups present and the counterion so that a broad range ofproperties is possible. Thus, while we have exemplified only thetriethyl quaternary ammonium and phosphonium salts, the quaternary saltswith other R groups are readily prepared to impart modified properties.Generally as the R groups become smaller (i.e. from ethyl to methyl),the ionic associations become stronger and more difficult to disrupt,but hydrophobicity improves as the R groups become larger. Propertiesare also strongly influenced by the counterion (i.e. chloride, bromide,bisulfate, etc.). Similarly properties of the S-isothiouronium salts arestrongly dependent upon whether thiourea itself is used (as used in ourexamples) or substituted thioureas are used as the nucleophile. Strengthof the ionic crosslinks and hydrogen bonding properties are bothdiminished as substituted thioureas containing more and longer R groupsare used to prepare the salts. Also the R groups themselves can containother functionality to prepare cationic salts containing other usefulfunctionality as for example, using instead triethanol amine as thenucleophile to prepare a pendant functionalized polymer containingquaternary ammonium salt groups with hydroxy functionality to permitfurther reactions or promote adhesion or dispersant action, etc.:##STR24##

In addition, although not exemplified herein, it would be obvious to oneskilled in the art that pendant artionic groups could also be attachedto prepare anionic pendant functionalized polymers such as carboxylatesor sulfonates.

Example 4 Preparation of Pendant FunctionalizedIsobutylene/Para-methylstyrene Copolymer Containing DithiocarbamateEster Functionality Example 4A

In this example, pendant dithiocarbamate ester functionality wasattached to a randomisobutylene/para-methylstyrene/para-bromomethylstyrene base terpolymerby nucleophilic substitution using sodium diethyl dithiocarbamate as thenucleophilic reagent. The base terpolymer containing the reactiveelectrophilic benzylic bromines was prepared as already outlined. Thestarting polymer was prepared as in Example 1; it contained 3.3 molepercent para-methylstyrene with a viscosity average molecular weight of68,000. The polymer was radically bromineted using light initiation at40° C. as a 15 percent solution in hexane to give a base terpolymer witha viscosity average molecular weight of 65,000 and containing 4.3 weightpercent bromine. The base terpolymer composition was 96.7 mole percentisobutylene, 2.6 mole percent para-bromomethylstyrene, and 0.7 molepercent para-methylstyrene. There was some dibrominatedpara-methylstyrene present because of the high bromination levelachieved. In the nucleophilic substitution reaction, 200 g of the baseterpolymer was dissolved in 2100 g of toluene in a 5 1 resin flask undernitrogen to form an 8.7 weight percent solution. Then 22 g of sodiumdiethyl dithiocarbamate dissolved in 700 g of isopropyl alcohol wasadded slowly with stirring at room temperature to give a 6.6 weightpercent polymer solution in a 75/25 toluene/isopropanol solvent blendwith 1.2 moles per mole of Br of the nucleophilic reagent. The solutionwas heated with stirring under N₂ at 80° C. for 6 hours to complete thenucleophilic substitution reaction before being cooled. However, samplesremoved after 1 and 3 hours showed that the reaction was already overafter 1 hour at 80° C. The cooled solution was given several waterwashes to remove the sodium bromide byproduct and other water solublesand then the polymer was recovered by precipitation and kneading inisopropanol as in the earlier examples. The polymer was dried in avacuum oven at 70° C. without added stabilizers since the attacheddithiocarbamate ester groups themselves acted as a polymer boundstabilizer. The recovered polymer was a tough slightly tannish elastomerwith complete solubility in hexane. Analysis as summarized below showeda very high conversion of benzylic bromine to dithiocarbamate ester hadbeen achieved.

    ______________________________________                                         ##STR25##                                                                     ##STR26##                                                                    ANALYSIS                                                                                               PENDANT                                                                       FUNCTIONALIZED                                                BASE TERPOLYMER COPOLYMER                                            ______________________________________                                        M.sub.v  65,000          65,000                                               Weight   4.3             0.6                                                  percent Br                                                                    Weight   --              2.97                                                 percent                                                                       Sulfur                                                                        Weight   --              0.65                                                 percent N                                                                     NMR                                                                           Mole percent                                                                           2.6             --                                                   benzylic Br                                                                   Mole percent                                                                           --              2.6                                                  dithio-                                                                       carbamate                                                                     ester                                                                         ______________________________________                                    

The proton NMR spectrograph confirmed the chemical analysis in showingthe quantitative conversion of benzylic bromine functionality to pendantdithiocarbamate ester functionality.

Proton NMR Resonances for Enchained Pendant Functional DithiocarbamateEster "Mer" Unit

    ______________________________________                                        PROTON                RESPONSE (ppm)                                          ______________________________________                                         ##STR27##            4.48                                                     ##STR28##            4.08                                                     ##STR29##            3.7                                                     ______________________________________                                    

This experiment showed that facile conversion of benzylic brominefunctionality in the base terpolymer to pendant dithiocarbamate esterfunctionality was possible via nucleophilic displacement. The attacheddithiocarbamate ester functionality provides built-in antioxidantprotection to the polymer as well as vulcanization and covulcanizationactivity and permits free radical chemistry to be employed as isdiscussed more later.

Example 4B

In this example a baseisobutylene/para-methylstyrene/para-bromomethylstyrene terpolymer wasprepared and converted via a sequential reaction route to a copolymercontaining pendant dithiocarbamate ester functionality without separateisolation and recovery of the intermediate base terpolymer. Thissequential reaction route which avoids recovery of the intermediate baseterpolymer is of course economically advantageous.

An isobutylene/para-methylstyrene random copolymer containing 2.4 molepercent para-methylstyrene with a Mooney viscosity of 30 (the samecopolymer used in Example 2A) was dissolved in hexane under nitrogen toform a 17 weight percent solution with 8 percent by weight of ATOMITECaCO₃ stirred in suspension as an acid scavenger to give an opaque whiteslightly viscous solution which was heated with stirring under nitrogento 60° C. The solution was illuminated with a 120 Watt spotlight andthen with continued stirring at 60° C. with slight nitrogen purge, 6.5weight percent bromine on polymer was added as a 20 weight percentsolution in hexane. The solution turned bright orange/red as the brominewas added but the color rapidly faded as the radical brominationreaction took place. Despite the opacity of the solution, thelight-initiated bromination progressed rapidly so that the bromine colorhad completely faded and the light was turned off within 5 minutes. Asample of the brominated solution was removed to enable characterizationof the brominated base terpolymer and then 1 mole of sodium diethyldithiocarbamate per mole of bromine was added as a 5 weight percentsolution in isopropanol to give an 80/20 hexane/isopropanol solventblend and the solution was stirred hot at 60° C. to effect thenucleophilic substitution reaction. Samples removed at 15 minuteintervals to follow the progress of the reaction showed that it wascomplete within 1/2 hour. The samples and final solutions were givenseveral water washes with dilute HCl (1%) to convert excess CaCO₃ toCaCl₂ and remove it and other water solubles into the aqueous wash, Thesolution was then washed several additional times with water to removetraces of acid before the polymer was recovered by precipitation andkneading in isopropanol as described in the previous examples.

In the first step of this sequential reaction, a portion of theenchained para-methylstyrene moieties of the starting copolymer wereconverted to para-bromomethylstyrene moieties by light initiated radicalbromination with the byproduct HBr being removed by reaction with thedispersed calcium carbonate: ##STR30## In the second step of thesequential reaction, the sodium diethyl dithiocarbamate nucleophilicreagent reacted with the electrophilic benzylic bromines to produce thedesired pendant functionalized product: ##STR31##

Analysis as summarized below showed that the intermediate baseterpolymer contained 1.2 mole percent benzylic bromine functionalitywhereas the final pendant functionalized product contained 0.9 molepercent dithiocarbamate ester pendant functionality with 0.3 molepercent benzylic bromine functionality remaining.

    ______________________________________                                                  ANALYSIS                                                                               INTER-     PENDANT                                                            MEDIATE    FUNCTION-                                                 STARTING BASE       ALIZED                                                    CO-      TER-       CO-                                                       POLYMER  POLYMER    POLYMER                                         ______________________________________                                        M.sub.v     280,000    280,00     280,000                                     Weight percent Br                                                                         --         2.0        0.5                                         Weight percent S                                                                          --         --         1.0                                         Weight percent H                                                                          --         --         0.2                                         NMR                                                                           Mole percent PMS                                                                          2.3        1.1        1.1                                         Mole percent                                                                              --         1.2        0.3                                         Br PMS                                                                        Mole percent                                                                              --         --         0.9                                         dithiocarbamate                                                               ______________________________________                                    

This mixed functionality polymer was stable without any addedantioxidants and was vulcanizable with promoted zinc oxide and/orconventional sulfur vulcanization systems. It also showed goodcovulcanization in blends with natural rubber. Films of this copolymercrosslinked on exposure to UV-radiation as opposed to the degradationnormally experienced with high isobutylene containing polymers exposedto UV-radiation. The crosslinking under irradiation is attributed to theready ability of the dithiocarbamate ester functionality to form stableradicals under irradiation to permit radical crosslinking and otherradical chemistry reactions to occur rather than backbone cleavage asnormally occurs with isobutylene based polymers: ##STR32##

This ability of the dithiocarbamate ester functionality to prevent UVdegradation and/or to impart controlled crosslinking under free radicalconditions is very valuable in exterior applications such as roofing,coating, white tire sidewalls, etc., where the tendency of isobutylenebase copolymers to degrade and develop surface tackiness has alwaysimpaired their utility in such areas.

Example 4C

In this example a pendant functionalized isobutylene based copolymercontaining nearly equal amounts of dithiocarbamate ester and benzylicbromine functionality was prepared via a sequential reaction routewithout recovery of the intermediate base terpolymer.

Five hundred grams of an isobutylene/para-methylstyrene random copolymercontaining 4.5 mole percent para-methylstyrene with a Mooney viscosityof 34 was dissolved in 2833 g of n-hexane under nitrogen a 5 l resinflask to yield a 15 weight percent solution. Forty-five grams ofOMYACORB UFT calcium carbonate was stirred in as an acid scavenger toyield an opaque white dispersion and then the solution was heated withstirring to 60° C. and illuminated with a 120 Watt spotlight.Thirty-five game of bromine (7 weight percent on polymer) was added as a25 weight percent solution in hexane to effect radical bromination andproduce the base terpolymer. The bromination reaction was over in <5minutes and after removal of a sample for characterization of the baseterpolymer, 30 g of sodium diethyl dithiocarbamate (0.9) moles/mole ofbromine) dissolved in 600 g of isopropanol (to give an 83/17hexane/isopropanol solvent blend) was added to effect the nucleophilicsubstitution reaction. The solution was stirred hot at 60° C. for 1/2hour to complete the reaction. After the solution was cooled and acidwashed, the polymer was recovered by alcohol precipitation as in Example4B. The sequential reactions proceeded as already outlined. Analysis assummarized below showed on intermediate base terpolymer with 2.2 weightpercent bromine and a final pendant mixed functionalized product with0.7 mole percent benzylic bromine and 0.7 mole percent dithiocarbamateester functionality.

    ______________________________________                                                  ANALYSIS                                                                                          FINAL                                                              INTER-     MIXED                                                              MEDIATE    PENDANT                                                   STARTING BASE       FUNCTION-                                                 CO-      TER-       ALIZED                                                    POLYMER  POLYMER    PRODUCT                                         ______________________________________                                        Mooney      34         33.5       33                                          Weight percent Br                                                                         --         2.2        1.05                                        Weight percent S                                                                          --         --         0.77                                        Weight percent H                                                                          --         --         0.17                                        NMR                                                                           Mole percent PMS                                                                          4.5        3.1        3.1                                         Mole percent Br                                                                           --         1.4        0.7                                         PMS                                                                           Mole percent                                                                              --         --         0.7                                         Dithiocarbamate                                                               Ester                                                                         ______________________________________                                    

These examples show that pendant dithiocarbamate ester functionality isreadily introduced into the base terpolymer of this invention by anucleophilic substitution reaction. Stable mixed functionality polymerscontaining both benzylic bromine and dithiocarbamate ester functionalitycan be made at any desired ratio of the functionalities and aneconomical sequential reaction route can be utilized.

Example 5 Preparation of Pendant FunctionalizedIsobutylene/Para-methylstyrene Copolymer Containing Various EsterFunctionalities Example 5A

In this example, pendant cinnamate ester functionality was attached to arandom isobutylene/para-methylstyrene/para-bromomethylstyrene baseterpolymer by nucleophilic substitution using a cinnamic acid salt asthe nucleophilic reagent. The base terpolymer used in this example wasidentical to that used in Examples 4A and 4B and contained 0.9 molepercent bromineted para-methylstyrene, 1.4 mole percentpara-methylstyrene, and 97.7 mole percent isobutylene with a M_(v) of135,000.

In the nucleophilic substitution reaction, 750 g of the base terpolymerwas dissolved in 3000 g of toluene in a 5 l resin flask with an attachedair condenser by stirring under N₂ to form a 20 weight percent solution.Next, 35.4 g of cinnamic acid (1.5 moles/mole bromine), 77.3 g of 40weight percent tetrabutyl ammonium hydroxide solution in methanol (0.5mole/mole acid) and 9.6 g of 50 weight percent sodium hydroxide solutionin water (0.5 mole/mole acid) were stirred in and the resulting emulsionwas heated to a reflux temperature of 86° C. under constant stirring.The solution was refluxed for 3 hours at 86° C. to complete the reactionwith samples removed at the initial reflux point and after 1/2 and 1-1/2hours of refluxing to monitor the progress of the reaction. The solutiongradually became clearer during the reaction. After three hours it was atranslucent, light beige color. The final solution and samples weregiven acidic, basic and neutral washes. Then the polymer was recoveredby precipitation and kneading in isopropanol as in earlier examples andvacuum oven dried at 70° C. with a 0.2 weight percent BHT mixed in as anantioxidant. Analysis was conducted using a Princeton-Gamma Tech Bromineanalyzer and is summarized below for bromine remaining in the startingpolymer against reaction extent shows that the nucleophilic substitutionreaction was proceeding slowly and had still not gone to completionafter three hours of refluxing:

    ______________________________________                                        Reaction Progression                                                                            Wt. % Bromine                                               ______________________________________                                        Starting base terpolymer                                                                        1.60                                                        At point of reflux                                                                              1.37                                                        1/2 hour later    1.08                                                        11/2 hours later  0.91                                                        (final) 3 hours later                                                                           0.54                                                        ______________________________________                                    

The final product following three hours of reflux contained 0.8 molepercent cinnamate ester and 0.1 mole percent benzylic bromine. Thenucleophilic substitution reaction was about 90 percent complete:##STR33##

Proton NMR spectoscopy was used to quantify the amount of cinnamateester functionality introduced:

NMR Resonance

    ______________________________________                                        PROTON                RESONANCE (ppm)                                         ______________________________________                                         ##STR34##            5.2                                                      ##STR35##            6.48                                                     ##STR36##            7.73                                                    ______________________________________                                    

with, of course, the new aromatic protons also being present in thespectrograph.

This experiment showed that pendant carboxylic acid ester functionalitycan be introduced into the base terpolymer of this invention bynucleophilic substitution under suitable conditions. The cinnamate esterfunctionality enables crosslinking to occur when the polymer isirradiated by actinic radiation.

Example 5B

In this example, pendant fatty acid ester functionality was attached toa random isobutylene/para-methylstyrene/para-bromomethylstyrene baseterpolymer by nucleophilic substitution using a commercial C₁₈ fattyacid in linolenic acid (INDUSTRENE 120 from Witco Corporation) as thefatty acid. The base terpolymer used had a Mooney viscosity of 30 andcontained 2 mole percent para-bromomethylstyrene, 5 mole percentpara-methylstyrene, and 93 mole percent isobutylene.

In the nucleophilic substitution reaction, 500 g of the base terpolymerwas dissolved in 2833 g of toluene in a 5 l resin flask with an attachedair condenser under nitrogen pad to form a 15 weight percent solution.Then 63.3 g of INDUSTREEN 120 Linseed fatty acid (1.2 moles/mole Br) wasadded along with 72.8 g of 40 weight percent tetrabutyl ammoniumhydroxide solution in methanol (0.5 moles/mole acid) and 9 g 50 percentNaOH solution in water (0.5 moles/mole acid). The emulsion that formedwas opaque and slightly yellowish. Next, it was heated to the refluxtemperature at 87° C. under nitrogen with stirring. The emulsion wasrefluxed for 2 hours with samples being removed at the reflux point,after 1/2 hour and after 1 hour of refluxing to monitor the progress ofthe reaction. During the reaction, the reaction solution became clearerwith water droplets being distilled over into the condenser. The finalsolution was translucent with a light yellow color. The reaction samplesand final reaction effluent were given acidic, basic, and then neutralwater washes before the polymer was precipitated in isopropanol andvacuum oven dried as before. Analysis below, as in Example 5A, forbromine remaining in the starting polymer indicates that thenucleophilic substitution with the C₁₈ fatty acid was faster than withthe cinnamic acid salt and was essentially complete in one hour.Apparently the carboxylate nucleophile attached to the C₁₇ hydrocarbonmore easily achieved necessary intimate contact with the benzylicbromine electrophile attached to the base terpolymer than thecarboxylate group attached to a shorter aryl group.

    ______________________________________                                        Reaction Progression                                                                            Wt. % Bromine                                               ______________________________________                                        Starting Base Terpolymer                                                                        3.0                                                         At Reflux         1.06                                                         1/2 Hour Later   0.45                                                        1 1/2 Hours Later 0.29                                                        (Final) 3 Hours Later                                                                           0.23                                                        ______________________________________                                    

NMR analysis showed that the final product contained 2 mole percentester and essentially no benzylic bromine indicating that thenucleophilic substitution reaction had gone to completion. (Smallresidual bromine content measured by the bromine analyzer probablyrepresented inorganic bromides not thoroughly washed out during recoverysteps). The NMR spectrum (below) shows a resonance due to the benzylicester protons at 5.08 ppm and a broad complicated resonance due to theolefinic protons in the C₁₈ chain at 5.3-5.5 ppm.

NMR Resonance

    ______________________________________                                        PROTON                RESONANCE (ppm)                                         ______________________________________                                         ##STR37##            5.08                                                     ##STR38##            5.35-5.55                                               ______________________________________                                    

In comparison, the benzylic ester protons of the cinnamate ester ofExample 5A showed a higher field resonance at 5.2 ppm due to theconjugation present in the cinnamate ester.

The fully converted linseed oil acid ester derivative of this exampleremained completely soluble and showed no evidence of vulcanizationcrosslinking when compounded and heated under typical vulcanizationconditions with zinc oxide or promoted-zinc oxide vulcanization systemswhich are effective with the starting bromineted "base" terpolymer andanother confirmation of the absence of any remaining benzylic bromines.The functionalized polymer, however, gave good vulcanizates whencompounded and cured with typical sulfur vulcanization system below:

    ______________________________________                                               Polymer 100                                                                   Sulfur  1.25                                                                  M. Tudds                                                                              1.50                                                                  Altax   1.00                                                                  Zinc Oxide                                                                            3.00                                                           ______________________________________                                    

The presence of unsaturation in the pendant fatty acid side chains thuspermits conventional sulfur vulcanization systems to be employed tovulcanize the functionalized ester derivative of this example. Thependant unsaturation is also useful in permitting covulcanization withthe high unsaturation general purpose rubbers such as natural rubber orSBR. Testing of sulfur vulcanized specimens of this ester derivative ina standard ozone resistance test showed that they retained theoutstanding ozone resistance characteristic of the saturated baseterpolymer vulcanizates. The pendant unsaturation in the side chain thusimparts conventional sulfur vulcanization activity without adverselyaffecting ozone resistance.

Example 6

In this example, pendant fatty acid ester functionality in which thefatty acid contained conjugated unsaturation was attached to the baseterpolymer. The fatty acid used was derived from Tung oil and was highin eleostearic acid. The base terpolymer had a Mooney viscosity of 32and contained 3.6 weight percent bromine, 2.2 mole percentpara-bromomethylstyrene, 2.7 mole percent para-methylstyrene, and 95.1mole percent isobutylene. In the nucleophilic substitution reaction, 666g of a "wet" base terpolymer crumb (500 g dry weight) were dissolved in283 g toluene in a 5 l resin flask with an attached air condenser toyield a 15 weight percent polymer solution containing dispersed water.This use of the "wet" crumb in the nucleophilic substitution reactionwas advantageous as it avoided the need to finish the brominated "base"terpolymer prior to converting it to the pendant functionalized polymer.To the polymer solution was added 76 g of Tung oil acid (-1.2 moles/molebromine), 87.4 g of 40 weight percent tetrabutyl ammonium hydroxidesolution in methanol (0.5 moles/mole acid) and 43 g of 50 weight percentsodium hydroxide solution in water (0.2 moles/mole acid) to give a milkywhite emulsion which was heated to a reflux temperature of about 84° C.The reaction mixture was allowed to reflux for one hour under constantstirring before being cooled, washed and recovered as previouslyoutlined. Samples removed at the reflux point and 1/2 hour later weresimilarly recovered.

The substitution reaction was proceeding rapidly under these conditionsas shown by the following bromine analysis:

    ______________________________________                                        Reaction Progression                                                                            Wt. % Bromine                                               ______________________________________                                        Starting Base Terpolymer                                                                        3.6                                                         At the Reflux Point                                                                             0.78                                                         1/2 Hour Later   0.56                                                        (Final) 3 Hours Later                                                                           0.40                                                        ______________________________________                                    

The NMR spectrum shows a resonance due to the benzylic ester protons at5.08 ppm, some residual resonance at 4.47 ppm due to remaining benzylicbromide, and a series of resonances at 5.3-6.4 ppm due to the olefinicprotons of the C₁₈ acid (with the conjugated unsaturation resonancesbeing the high field resonances at >5.9 ppm). The final productcontained 1.9 mole percent ester with 0.2 mole percent benzylic bromideremaining. It was completely soluble in toluene with a Mooney viscosityof 31 which was the same as the starting base terpolymer.

Despite the highly active nature of the pendant conjugated unsaturation,this functionalized polymer showed good stability with no tendency tocrosslink during drying or storage. However, the attached conjugatedunsaturation permitted facile vulcanization and covulcanization withunsaturated rubbers using sulfur vulcanization systems. The conjugatedunsaturation also provided good crosslinking under electron beamirradiation and oxidative surface curing upon outdoor exposure tosunlight. This is a highly desirable property in exterior coatings suchas roof coatings. The conjugated unsaturation is also very active inradical reactions thus permitting grafting reactions with free radicalpolymerizable monomers. This highly active Tung oil acid esterderivative is useful in a wide range of applications.

It is obvious that nucleophilic substitution reactions with variouscarboxylic acids could be used to attach many other functional sidechains such as hydroxy using ricinoleic acid, etc.

Example 7

Starting with a baseisobutylene/para-methylstyrene/para-bromomethylstyrene terpolymerintermediate similarly prepared to Example 1, the UV photoinitiatorbenzophenone was incorporated into the terpolymer as a 4-benzoylbenzoateester derivative.

A 250 ml glass reaction vessel, fitted with a mechanical stirrer, a hoseconnector, and a septum purged with nitrogen, operating in an atmosphereof nitrogen, was charged with 10 g base terpolymer (Mooney viscosity 32,1.88 weight percent bromine), dissolved in 80 ml toluene. In a secondflask, a toluene solution of tetrabutylammonium and 4-benzoylbenzoatewas prepared under nitrogen by dissolving 0.51 g 4-benzoylbenzoic acidand tetrabutyl ammonium hydroxide (2.2 ml, 1M in methanol) in 25 mltoluene, then reducing this solution by one-half its volume. Next, anadditional 0.09 g 4-benzoylbenzoic acid was dissolved in 25 ml tolueneand added dropwise until the second solution was weakly basic. Thissolution was then added to the first. The temperature of the mixture wasraised to 70° C. and allowed to react for 6 hours. Upon completion, thepolymer was precipitated from methanol and dried in a vacuum oven at 1mm Hg, 40° C. Analysis for 4-benzoylbenzoate content (NMR, IR) showedcomplete conversion of the 4-bromomethylstyrene to the 4-benzoylbenzoateester. The functionalized polymer had Mooney viscosity of 32 andcomprised 0.75 mole percent 4-benzoylbenzoate ester. Films (1.5 mil)were drawn onto release paper then exposed to UV radiation. Thefunctionalized polymer showed good crosslink response at low absorbancelevels as seen in Table I.

Examples 8-11

In the following examples, 3 -benzoylbenzoate (Example 8),2-benzoylbenzoate (Example 9), 4-hydroxybenzophenone (Example 10), andanthraquinone-2-carboxylate (Example 11) derivative functionalizedcopolymers were prepared in nucleophilic substitution reactionsaccording to the procedure in Example 7 to incorporate thephotoinitiators benzophenone, hydroxybenzophenone or anthraquinone. Thebase isobutylene/para-methylstyrene/para-bromomethylstyrene terpolymerwas the same throughout, similarly prepared to the procedure in Example1, and having a Mooney viscosity of 32 and 1.88 weight percent bromine.The UV-functionalized copolymers comprised 0.75 mole percent ester. Ineach reaction, 2.0 g base terpolymer was utilized. The initial quantityof 3-benzoylbenzoic acid reactant was 0.11 g followed by an additional0.02 g to neutralize litmus paper. The quantity of 2-benzoylbenzoic acidutilized was the same as for 3-benzoylbenzoic acid. The quantity ofanthraquinone-2-carboxylic acid utilized was 0.12 g and the quantity of4-hydroxybenzophenone was 0.09 g.

Films (1.5 mil) were drawn onto release paper for gelation studies. Thedata in Table I show outstanding crosslink conversion at low UVabsorbance levels for the photoinitiator-grafted polymers for theseexamples also.

                  TABLE I                                                         ______________________________________                                                        PERCENT GEL                                                                   FORMATON.sup.1                                                                LEVEL OF UV EXPOSURE                                          EX-    TYPE           (J/CM.sup.2)                                            AMPLE  FUNCTIONALITY  0.1      0.2    0.4                                     ______________________________________                                        7      4-benzoylbenzoate                                                                            94       95     95                                      8      3-benzoylbenzoate                                                                            90       89     89                                      9      2-benzoylbenzoate                                                                            68       82     79                                      11     anthraquinone-2-                                                                             83       85     88                                             carboxylate                                                            ______________________________________                                         .sup.1 Percent insoluble materials after toulene extraction              

Examples 12-19

To the cinnamate functionalized copolymers similarly produced in Example5A, tests were performed to determine the level of gel formation atvariable coating thickness and UV-exposure. The base terpolymer had aM_(v) of about 135,000 and was made up of 2.3 mole percentpara-methylstyrene including 0.9 mole percent brominatedpara-methylstyrene. It was converted via bromination and subsequentnucleophilic displacement into the polymer of Example 5A which contained0.1 mole percent para-bromomethylstyrene and 0.8 mole percent cinnamateester. The cinnamate functionalized copolymer was crosslinked via a UVinitiated 2+2 photocycloaddition with the results appearing in Table II.

From the data it can be seen that the highest degree of crosslinkingoccurred in thin coatings with high UV exposure and low weight percentfunctionalization.

                  TABLE II                                                        ______________________________________                                             MOLE                   COATING                                           EX-  PERCENT   LEVEL OF     THICK-  GELATION                                  AM-  CINNI-    UV EXPOSURE  NESS    (% OF                                     PLE  MATE      (J/cm.sup.2) (mil)   POLYMER)                                  ______________________________________                                        12   0.8       0.3          0.09    44                                        13   0.8       0.3          0.17    51                                        14   0.8       0.3          0.25    34                                        15   0.8       0.3          0.42    19                                        16   0.8       0.6          0.14    69                                        17   0.8       0.6          0.17    73                                        18   0.8       0.6          0.37    64                                        19   0.8       0.6          0.57    36                                        ______________________________________                                    

Examples 20-21

In the following examples, the 4-hydroxybenzophenone functionalizedcopolymer from Example 10 was utilized as corrosion barrier coatings ongalvanized steel plates. Initially, the Example 10 polymer was dissolvedin toluene then coated onto 2 galvanized steel plates. Evaporation ofthe solvent provided a 1 mil thick film coating. One plate wascrosslinked by exposure to 0.24 J/cm² UV-radiation and the other was notcrosslinked. After 10 days immersion in a 5 percent NaCl salt bath, theplates were observed for corrosion resistance. Both coatings protectedthe galvanized steel plates from corrosion, but the plate withuncrosslinked film showed corrosion intrusion under the outer edges ofthe coating. The advantages of crosslinking the coating are improvedresistance to corrosion and non-polar solvents. Potential applicationsfor such material include corrosion protection in the automotiveindustry.

Example 22

In the following example, the 4-hydroxybenzophenone functionalizedcopolymer from Example 10 was utilized as a coating in a lithographicapplication. A 1 mil film was coated onto a cardboard substrate asdescribed in Examples 20-21. The dried film was irradiated with 0.25J/cm² UV light through a photographic negative to produce a stenciledimage in the coating. The image was revealed by developing in toluene toremove the uncrosslinked polymer.

The foregoing description of the invention is illustrative and variousmodifications will become apparent to those skilled in the arc in viewthereof. It is intended that all such variations which fall within thescope and spirit of the appended claims be embraced thereby.

What is claimed is:
 1. An article having a barrier coating resistant tocorrosion and solvents made by(a) coating at least a portion of asurface of an article with a composition comprising a random copolymerof an isoolefin of 4 to 7 carbon atoms and para-alkylstyrene comonomer,said isoolefin comprising 10 to 99.5 weight % of said copolymer and saidpara-alkylstyrene comprises 0.5 to 90 weight % of said copolymer,wherein about 0.5 to 55 weight % of said copolymer comprisespara-alkylstyrene monomers having a photo-initiator substituted on thependent alkyl group, said copolymer having a substantially homogenouscompositional distribution; and (b) exposing a portion of said coatingto gamma, UV, electron beam, visible, or microwave radiation tocrosslink the copolymer.
 2. The article of claim 1 further wherein saidcoating is etch-resistant and patterned.
 3. A surface havinglithographic image thereon made by(a) applying a coating to at least aportion of a surface of an article with a composition comprising arandom copolymer of an isoolefin of 4 to 7 carbon atoms andpara-alkylstyrene comonomer said isoolefin comprising 10 to 99.5 weight% of said copolymer and said para-alkylstyrene comprises 0.5 to 90weight % of said copolymer, wherein about 0.5 to 55 weight % of saidcopolymer comprises para-alkylstyrene monomers having a photoinitiatorsubstituted on the pendent alkyl group, said copolymer having asubstantially homogenous compositional distribution; (b) selectivelyexposing a portion of said coating to gamma, UV, electron beam, visible,or microwave radiation to crosslink the copolymer, thereby forming acrosslinked latent lithographic image; and (c) removing theuncrosslinked copolymer to develop the lithographic image.